rotating heavy use bikes

The bike I taught on is the one bike in the gym cycling studio that always gets used. . . the instructor's bike. It started making a funky chain grinding noise last night in the second half of my second back to back class, so I dismounted the bike, pushed it off to the side and pulled a new one up for me to use. I spoke with the management about occasionally rotating the bikes, before they have a problem. Are there bikes that almost always get used, due to positioning, mirrors, air con, fans, speakers or whatever? I think it is worth considering letting your bikes age together, rather than killing a few bikes (namely the instructor's bike) more quickly. maintenance, maintenance, maintenance - keep an eye on the quality of your bikes. . . next to your instructor, it is your major asset.