This seems to be a thread about whether we ease and reset our topping lifts every time we raise and lower the mainsail. At least on my boat, the topping lift is set so that it is loose enough to sail whenever the mainsail is hoisted, no matter how hard I haul in my mainsheet, and I never adjust it otherwise. Consequently, I have to ease my mainsheet or I can't haul my sail up. Its that simple.
That said my halyard winch is near my mainsheet so I keep the sheet tight until the mainsail is halfway or more up before releasing the sheet.
Obviously, if you ease and tighten your topping lift with each mainsail hoist, then it doesn't matter one way or the other whether you release the mainsheet when you hoist the mainsail. Except that, with the mainsheet tight, most boats will weathercock into the wind when the sails are almost up, making it easier to finish the hoist.
Jeff