Many parents/gymnasts have come and gone through the years. While most I keep a distant friendship with (say hi when you meet up at meets and an occasional text or FB message), one of my best friends switched gyms more than 4yrs ago. I've found that she gives me a more rounded view of what's going on. Say, if I'm frustrated with how something at my dd's gym is going....she's "knows" where I'm coming from and what's upsetting me because she's been at my dd's gym.....but she also has an outside perspective to give. I can do the same for her (even though we haven't been at their gym...I can give a different point of view for her). Our girls are all within a few years and are the same levels. We are good for each other I think.
For a friendship to last through gym changes, BOTH parties have to want to keep the friendship. If a switch occurs, both parents have see past a possible rivalry (if the gym switched to is close by....it can be tough).
There are other parents who've left that quite frankly, they were never my friend when our kids were on the same team...why would I seek to make a friendship now after they've left?
