Depends on the setup. For small boxes, and small drawers, not so bad. I have 30 or so to deal with, several 72x30 drawers, meaning they need 100% unloaded. Even some of the 36x30 need unloaded. I just spray them with some penetrating oil if they ever feel sticky. A couple of cycles smooths them right out. Now, these are modern ball bearing snap-on slides. If they get problematic, I just warranty them.
For my old snap on boxes with friction slides, I cleaned the rails and guides in the box/drawers, and scuffed some candle wax on the slides themselves. Worked pretty well, but it's a home box. Smelled like candle wax though, who'd have thought?