I'd leave it without adding casters. Just an Ol' Goat's observation.
With casters on it - someday, sometime or another you will go to plant your arse on it and it'll be just a bit 'off' and scoot out from under you.
Then it is tailbone against concrete, whilst your hands are occupied and you have no way of breaking your fall.
Takes a while to heal, and I was in my 40's then... -Just saying.