My sister rescued a Gsd bith 20mths ago she came to my sister in terriable condition weighing in at only just 21 kilos, the intention has always been to have Storm spayed the previous owner/breeder told them to wait till she has her season as she was due so waited they have now after 20mths in her new home Storm has finally come into season (day 1 today).

Their question is when should Storm be spayed (they have asked previous owner/breeder by she remains silent lots of other issues were discovered after they got Storm so relations are to put it midly strained!!) I know most vets say to wait 3 months before spaying but we have no idea when she will next come in. I own this bitches auntie (Arin) who had terriable trouble with season and her last one was so bad it has made a serious inpact on her (she is now noise phobic skittish and highly strung!!! she was fine before she had seasons) Arins mum Storms grandmother also had the same problems and was on hormone injections to get pregnant, we really dont want Storm to have to go through the same. What is the earliest Storm can be spayed after her season or is it better to wait the recommended 3 months and hope she dosnt come back into season (Its what Arin did).

I would still recommend counting 12 weeks from the first day of her season as being the best option.

However, I have a bitch who has always had "odd" seasons, and she has just had one after 16 months.  I was offered injections so that I could get her pregnant, but refused.  My grounds being that a bitch should conceive naturally, so she has never had a litter. 

My vet has offered to spay her 10 weeks after the start of this last season.  So I have agreed.

It is recommended to be mid way(but that can depend on how long inbetween a bitch goes), which is why ideally 3 months after. This is come about as you count 2 months from any possible mating, then extra time, depending on if a bitch is susceptable to phantoms or not?? I do usually manage to get our vets to spay slightly earlier than they want as I say I can guarantee 100% the bitch hasnt been mated, therefore no pups are inside!!

Given the dates you have quoted, it wont be before 27 Sept, so I would book her in around 2nd week of Oct(depending on a phantom??), which will mean you will have to delay it.

Please don't worry too much about seasons.  It sounds like you are seeing them as the cause of horrible problems.  Whereas it could just be that, for some reason, your previous dog was particularly sensitive to a specific noise.  That could be related to her cycle, since dogs can be more sensitive at different points in it - but to jump to the conclusion that you should have spayed before any seasons, just because a cycle can sensitise a dog sometimes, is a bit like saying all humans should have an ovariectomy to prevent those few with PMT from having it.

Seasons are a normal part of an adult female dog's life, and they do have effects - but please don't jump to the conclusion that 1) all the effects are bad and 2) you should avoid seasons or 3) that what was right for one of your dogs will necessarily be right for another.

There is much research to show that actually dogs which remain intact to the age of 6/7 years live much longer (on average) than dogs spayed early.  This is because exposure to the ovaries confers health benefits on the dog.  This same effect is present in humans - which is why women live longer than men.  If spayed, you remove this advantage. 

Furthermore, there are many instances where people have spayed and seen behavioural problems immediately worsen. 

It is a bit more complicated than panicking about your previous dogs' experiences and jumping to the conclusion that you should spay every dog you have asap.

Reading:
http://www.gpmcf.org/respectovaries.html
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2805875/?tool=pubmed
http://www.vizslacanada.ca/SNBehaviorBoneDataSnapShot.pdf
http://www.naiaonline.org/pdfs/LongTermHealthEffectsOfSpayNeuterInDogs.pdf
http://www.caninesports.com/SpayNeuter.html

The only reason i brought Arin my bitches problems up in regards to Storms seasons is because Arin seasons DID cause huge problems to my girl (i understand that Storm might not follow suite but there does seem to be a problem in these lines, My girl is not the only one to have these problems).

We are in no way in a panic about Storms seasons we just wanted to know at what point is the best time to spay her (as my sister promised Storms previous owner/ breeder she would be spayed) I am also in no rush to spay all my girls just because of my experiance with 1 of my girls but i do feel that the problems Storms grandmother Arins mother had have made an inpact and have caused the problems i have experianced.

Is it usual for a bitch to go 20 months inbetween seasons??

You don't say how old Storm is?  Or was when you got her? 

No, 20 months between seasons is very uncommon.  But as you said she was extremely out of condition when you got her and very underweight, perhaps this had an effect on her cycle - in the same way that anorexic girls stop their periods.  Once she'd regained her condition, perhaps her seasons restarted.  Who knows...

If you do want to spay her, you want to do so at the point in the cycle when her uterus is inactive - not when it is immediately after or immediately before a season.  This is not essential - plenty of bitches are spayed at other times just fine, since people don't always know when a dog's last season is when it comes into rescue for eg - but if possible, that's when it should be.  Waiting at least 3 months should mean that she enters that inactive time, even if the time between her seasons is longer.

Storm is now 4 1/2 years old my sister got her 20months ago, yes i totally agree about her condition being a factor with regards to her season it took a year for Storm to regain the condition she lost while with previous owner/breeder. We dont know how long it has been since her last season only that her owner said she was due when my sister got her!!.