I post on a lot of forums where people are growing long hair and many of them do not trim very often and some wait a few years like you.
There are some things to consider though. As far as trimming hair there are only two reasons to ever cut hair.
1. You have damage on your hair that you want to remove to prevent it from spreading further up.
2. To reshape your hair or make it shorter.
In both cases no matter what a stylist tells you it is still your choice as to how much gets cut off. Just because something bothers a stylist it doesn't mean it's bothering you. Yes damage can spread but if you don't want to cut it all at once you can cut some now and cut some later.
Have you been using any perms or colors or other harsh chemicals in the past few years?
Have you used any hot irons, blow dryers, or other hot tools and if so how often?
Do you think you need more than 1 or 2 inches trimmed?
Do you have split ends or damage higher than 2 inches from your ends? If yes is it a lot or do you think you could trim those hairs yourself?
Many people with long hair do sessions where they take a pair of good scissors, preferrably meant for hair, and they will go through and snip off the split ends. I realize that that sounds overwhelming if you've never gone through your hair strand by strand but I have a method that makes it easier.
First get yourself a piece of paper or a notebook or something you can write or type on. Then write down something like this. A calender could work too.
Right
Left
Top back
Bottom Back
You are going to be working on just one area of your head at a time. Lets pretend that you are using the 4 sections above. The first week you only do hairs on the right side. the next week only left. and so on. Then after you get through all 4 weeks or whatever number you have you start over again.
So lets say this week is Right side week. You have a whole week to do nothing but work on that side. If you have clips or bands or similar you can section your right side into smaller sections. Then you can do the right front first. Then the right middle. And so on. If you use the sections then you can stop and then return to that section later. Even if you have to take the clips or bands out and go do something else.
When you go through the hairs if you see a hair that you think is split or damaged snip just that hair above the damage.
If you follow this process for a few weeks you might find that when it comes time to do the same area for the second or third time that it's really hard to find any splits or damage. That will be because you got most of it. But don't panic if you do see some still. Just get rid of them.
Now since you have the higher stuff being trimmed off you can go to a stylist and get just the small regular trim such as 1/2 to 1 inch.
If you don't want to take a chance on a stylist talking you into more than you asked for you can try this method that many longhairs use.
Feye's Self Trimming
http://feyeselftrim.livejournal.comI've used it myself for a few years. Just be sure to use hair scissors or shears and when you try that method for the first time only try an inch or less. That way if you do need some fixing it won't be too bad.
If you are sitting in a stylist's chair remember that you are the boss. If they cut more than you asked do not pay. If you do not already have a stylist then call salons and specifically ask for a stylist who will listen to you and do what you ask. Or visit the salons and ask the stylists. Many salons offer free consultations. This is a chance to talk to a stylist about your hair without committing to a service. If you go to a consultation and you feel pressured at all then they probably should not be your stylist.
Hope this helps.