I see some people that shoot lights out with their tip rolled over the ferrule pretty good, and It simply amazes me at times that it does not effect them. Wish I was the same, It doesn't matter whether It's mental or physical with Me It bugs the heck out of me and I can't play worth a darn until I fix It. My understanding is that this is the case for most people. I won't go into what all It causes, as It's pretty much the same as has been mentioned here already.
I think most people offer free trimming on their own work. I am no different, I offer It as a free service as well, but usually no one takes advantage of It until they are ready for a cleaning. Unfortunately too many people take It upon their self to sand the tip flush with the ferrule, and that's a bad habit to get into IMHO. I see a lot of overly tapered ferrules as a result of this. The only option for obtaining the tip diameter back where It was is to shorten the ferrule or replace It completely when this happens.
I recommend that people take advantage of the free trimmings that some of us offer, as It is all part of breaking the tip in properly. It only takes a minute or 2, and the ferule is barely touched if any at all in the cases where It's cleaned up a bit also. Most tips will do It at least once, with the rare exceptions of a few that are real good about not mushrooming. Some may do It twice or more, and that really depends on how much time is spaced between the install and initial trimming, and/or the type of tip, but in general If they require more then 2 trimmings on average, then I think I would consider a new tip, but that's just My personal opinion. There are things we can do to minimize mushrooming, but the majority of tips will still require a minimum of one trimming.
Like I mentioned at the top, I'm one of those that can't stand my tip to be mushroomed, and I do feel it has many bad effects on contact with the cue ball the same as everyone else, but I still feel It's a bit subjective, cause sometimes It just ain't the cue, It's the person or mindset, and things like that don't effect them like most people that put too much thought into things like that, They can pick up any ratty cue off a bar room wall and take down anyone in the house regardless of what the opponents are using. I see this all the time, and on occasion I have picked up a bar cue instead of My own, even in an attempt to even My speed out with someone else's or simply cause I didn't have My case of cues with me at the time. On many occasion I surprised Myself, but then again, I only took one look at the crappy tip, ferrule, noticed that maybe the weight doesn't suit me, but after that I never looked Back, I was more worried about adapting and making It work for me.
The difference in My personal cue I think is that I expect more from It, I expect it to perform and do most of the basic work, therefore if a shot veers off to one side, It miscues a lot, or the cueball doesn't go where I expect, I start looking at My tip for a problem or mushrooming. I also tend to keep a really good Eye on It when I'm not having having a problem with It, and If I start seeing a mushroom, It effects My shot confidence a great bit. That I think makes It become more of a mental issue for me, then the actual physical effects caused from the mushroom itself. Most of the people I see that are not really effected my It, Pay no attention to It at all. others are like Me and it drives them nuts, they are constantly sanding their ferrule away at any small sign of a mushroom. I have the luxury of a lathe at home, so I wait to get home, and then just trim It with a razor, But If I didn't have that I'd probably be in the same boat.
Just My thoughts here, none of It is written in stone Yet, They said it all wouldn't fit onto one tablet
