I'm not sure what you mean when you say, "More and more apps now are starting to require Catalina."
Obviously many popular third party apps have released Catalina compatible 64bit versions if they weren't already but I can't think of any that require Catalina.
If you have portable/peripheral devices such as iPad, iPhone, Apple TV which you may find, if they are updated, will have added functions once synced with Catalina.
I cannot say if upgrading will effect battery time.
What I would say is what I say to everybody considering upgrading their macOS;
make a bootable, cloned copy of your existing internal drive.
So if the upgrade goes pear shaped or you simply don't like it you can boot from the clone, erase your HD (you have to do this because Apple will not let you go backwards ie. you can't install Mojave from Catalina) then you can clone the copy back onto your erased HD and it will be exactly the same as it was at time of cloning.
Be aware you cannot do this with Time Machine.
I personally use Carbon Copy Cloner (Bombich Software), there are others such as SuperDuper.
Both offer 30 day fully functional obligation free trials.
Be sure to test your clone to make sure it is bootable before you upgrade. It will be slow from an external USB HD but it will boot eventually.
Once you're happy that its bootable you can go ahead with your upgrade with the knowledge that you can always go back or try again.
