Hello and welcome to just answer.
The TSBs don't have any time limits but they do normally become archived and removed from the computer system. Also just because these come up when you car details are put in to the computer it doesn't always mean that they have to be carried out on your car.
The are there for when you have any sort of problem with your car and it's a reference that the garage can check to see if there is any known issue.
For example if you had a misfire on your car and this was a known issue there would sometimes be a TSB for it and if it applied you could then carry out the work described in it. However if your car is running perfectly fine and has no issues then there would be no reason to have any of the TSBs carried out.
They are not the same as a recall as recalls target certain vehicles and they would normally contact the owner or it would be picked up when you have the car repaired at a dealer and the recall would then be carried out with no cost to yourself. Even if your warranty has expired the recalls are still done free of charge.
I hope this helps to clear this up for you but if I can help further please feel free to ask