Phasing young chins into longer playtimes/wheel

In a couple weeks, both our chins will be 6 months. We've been giving them 10 minute play times a couple times a week, as people here suggest not overdoing it when they're young. We are going to start giving them longer play times, my question is, should we go in phases, to get them used to it? As in, should we do 15 minutes one playtime, then 20 the next, then 25, etc? Do you ease them in, or is it safe at this point to just let them have a long playtime?

We will also be putting in a chin spin. Will we need to monitor this, as they're still pretty young, or can we assume they'll likely be safe since they've reached 6 months?

Thank you!