If traffic is light, and your flightplan won’t interfere with other aircraft, we usually let you follow it all the way in.
A few things to be aware of…
Your flightplan needs to make sense for the approach you’ve asked for. For example, If you ask for an ILS approach, and your flightplan doesn’t provide a reasonable entry to acquire the localizer, we will pull you off the flightplan and vector you in with a heading that is appropriate for the runway.
If it’s very busy, we may pull you off and line you up in a pattern we’ve created to help manage spacing. It is possible to let a few people fly their patterns, and zipper others in around them, but that usually results in less than optimal spacing. The patterns we use when traffic is heavy are designed to provide many points where we can modify spacing.
You may also have your runway changed. If busy, and you’re arriving from the north but have asked for the south runway, we may change you to a runway better suited for a north approach.
So you can see there are many reasons why we may move you off your planned flight.