That you are making this kind of progress in 3 months puts you ahead of many people here in the same boat.

I would say that if you start playing a song and you can make the changes in time... without warming up with a lot of chord changes... You are proably already in command of chord shapes, You will probably also find that you now have a developing Muscle Memory. Congradulations, this makes you a real nacent guitar player.

Your playing songs that use those chords will likely suffice to keep that Muscle Memory tuned and ready. If not, it is easy to throw some chord change exercises. I suspect that soon you will be letting go of those exercises and replacing them with MUSIC. ONCE AGAIN CONGRADULATIONS. THIS IS A BIG DEAL.