Quoted from gweempose:
I've never really understood why these protectors are necessary. I own some heavily routed games that are 20-25 years old, and the playfields are still quite nice. I can understand some cliffys or mylar here and there, but a full playfield protector just seems like overkill on a game that will be in a home collection its entire life. I'm assuming they also change the way the ball rolls, which would be another negative.
I played a bunch of games with my star trek before and after. the same with my medieval, The only real difference I noticed was there was less spin. I could of been imagining that though. if anything it plays a lot faster, most new sterns have tons of uneven levels on their playfields and of course mylar that tends to hang the ball up on occasion.
Also if you've seen some of the new sterns after they have been at these free play places for a month, the dimples on those things are crazy. All the other manufactures have them to, but they are much less noticeable. This goes to what type of quality of wood they are using on their playfields. slow grown/fast grown, pine, oak etc..
granted a routed game will get played a lot more, but still...
These are expensive toys, and a protector gives piece of mind. I have them on all my games (most), mainly in case I'm not able to clean them for a prolonged period of time while they are on location. Think the biggest benefit is the resale value, for a 100 bucks and 4- 12 hours of time that aint bad.