I have a two year old springer spaniel bitch who like all springers, I imagine, is pretty hyper active and will retrieve a ball all day long.  She happily runs alongside a bike or retrieves a ball constantly during a long walk without showing signs of tiredness.

However on days that are even slightly warm - say mid teens - she often lies down in a shady spot or even in a puddle - until I throw another ball or catch up with her etc. I'm slightly concerned about this behaviour. She will do it within say 20 minutes of starting the walk so I wouldn't have thought it could be tiredness and its on days which really aren't (in my opinion) Particularly warm.

Should I be concerned?? She is due her yearly checkup next month and I will obviously mention it to the vet but wondered if I should get her seen now.

Any thoughts?

I think it would be a good idea to tell your vet when you go to see him.
My last GR tended to behave in the same manner all her life. She learnt that shade meant a cooler spot and would run ahead and lie down in the shade or long cool grass until we caught up, always in and out of water cooling off. I always thought she just felt the heat and liked to be cool, after all she had a long furry coat.
When she was about elevenish, she staggered about and collapsed one day whilst out for a walk on a warm day. After investigation it was found she had very enlarged heart and received medication which helped enormously and she lived another three years. I've often wondered if she had had a heart problem for a lot longer given her need to keep cool on warm days.
I hope I haven't scared the bejabers out of you, but as her behaviours a bit unusual it would be worth seeing if your vet shares your concerns

A bit scary to read yes but I do appreciate the response.  Will definately get vet to check her heart. Thanks again.

No harm in getting her checked, but my girl of 18 months is exactly the same, running after balls all day if she could, she seeks out puddles or sea water at the beach to cool off regularly, and she was checked by the Vet quite recently and is very healthy.  Hope your girl is the same.  :-)