I just bought a second scope because I use the same gun with different barrels for deer and turkey. Slugs in the fall, #5 shot in the spring. I got tired of having to re-zero when I change seasons. The mounts are easy enough to change out. I will shortly be putting my new scope on and sighting it in with some cheap bird shot, then zeroing it with the load I expect to use this spring. I patterned my gun with 2 different chokes and 3 or 4 different brands of shot in a couple of different sizes last year and I pretty much know what will pattern well now, its just a matter of ensuring the sights are on. I consider sighting in and patterning 2 different things. Of course, I may try patterning with different loads I haven't tried before or if I acquire a new choke tube, but if I use the same tube and same loads as last year, just making sure the scope is on is all I plan on doing.