How big are they and what size pots are they in? Usually repot when the roots are coming out of the bottom of the pot. Go up one or 2 pot sizes but no more is the rule of thumb.

That's a good indicator - when the roots protrude from the bottom change the pot. I once had a Sansevieria plant explode out of its pot in the middle of the night with such force, shards of terracotta flew across the room in all direction because I kept putting it off. I thought it was a bomb.

Paul you made me laugh! But I don 't suppose it was funny at the time...Newcomer, when you choose to repot make sure to avoid those rather fancy shapes with small bases because they are not stable when it gets very windy.
John Innes no 3 is probably the best compost for pot grown fruit trees.

Thank you all for your answers.