Most don't last very long before peeling or scratching. Weeks to months. It's something that someone wanting to sell inflicts onto the new owner to make it look fresh rather than doing the complete replacement that it really needs.

I mostly agree with the above...but not all methods are equal.

About 12 years ago we had our bathroom tile sprayed (pink 4x4's in both the tub area and wainscoat around the rest of the bathroom that had 1/16 grout lines. We expected it to last a year or more, but it's held up well and we still have it in the main (high use) bathroom. One has to be careful when recaulking since a paint scraper (razor blade) will peel it up. No peeling otherwise. BTW, everything has to be solid before you do it. I believe it was a spray urethane. Really potent smelling stuff. They tented the area, vented to the exterior, and masked everything not getting paint. We left the black trim unpainted so we now have a white/black motif in there. One day job at that time, three finish coats. I think it cost around $700

I am trying to remember if we did the tub, too. Probably not, but not sure.

Note, most guys nowadays will come out to do a quick, wipe-on fix for the tub. That looks awful, shows brush strokes, and doesn't last.

DS/DIL had a tub in their previous home done and it still looked great 3 yrs later when they moved.
They then had the guest bath tub done in the current home and 5 years later it still looks like new. The tub is used daily by their child......with bath toys always in the tub.

Research the methods and ask what guarantees are offered. In their home, the guy took most of the day, sealed off the area and used a spray technique.
They were asked not to use the tub for 1-2 days (if I remember correctly!)
I believe there are only 2 major companies to choose from, Miracle Method or Permaglaze. DS ended up using Miracle Method.

http://www.miraclemethod.com/bathtub-refinishing.htm

Here is a link that might be useful: Permaglaze