
What you decide to do re boosters would, for me, to a great extent depend on the local dog population where you are. Living here on the N.Cornwall coast, we have a huge number of incomers during the summer, all potentially bringing whatever into the area with them. So, whereas in the past when we lived in a quiet rural area, I've dropped off boostering at all by around 7 years, I may think differently with my current two, living here.
My puppies were always given the full course of vaccination, followed by booster 12 months on. This is what I did with my current two but they are now both on 3-yearly boosters, apart from the one for Leptospirosis which is said to 'drop off' over 12 months. This is done annually still.
Interesting about the tumours because my Whippet had a small pea-sized mass taken off just before Christmas. The fine needle aspiration wasn't sufficient for a conclusive result, so I was persuaded to get it taken off anyway. Right now I have a Basset with two incisions, on either side, shoulders. The one was checked originally but booked in because it was growing. It was clear. Between the surgery date and that day, I felt another on the opposite side which was also growing. This one was deeper, and could be a nasty. I held off having them send the tissue they took off away (lots going on in my personal life at the moment and do I NEED to know!!), but have been persuaded to get it done, so they learn more about what it was and whether they need to revisit the margins they have taken. Mine is a breed (the Basset) prone to these fatty cysts, which is what they normally are, not mcts and in truth my Basset has more little tumours on his body. Whether there is a connection between these and boosters I have no idea. I'd suggest not? I have had these on my Bassets over the years, and tend to leave alone unless they are in a difficult place, or grow significantly. And indeed with one, fast as we took one off, another would appear in another place.
I don't do more boosters than I feel necessary!!