The downside to too much stabilizer is that you have to keep your chlorine extra high to keep algae at bay. You're not going to get a definite answer on what is the absolute upper limit. We typically recommend 30-50 for most pools, but there are many people who intentionally run with a higher cya than that. One of my co-moderators, Janet (Aylad) does just that because she says that with her location (Louisiana) and the amount of sun her pool gets each day, it makes it easier to manage her chlorine consumption. Probably the best thing for you to do is to repost with a current set of water testing results and let somebody here take a look. That will help you get better advice. Welcome to the forum!