You are right,leaves typically have an approx life of two years,so it could be normal.I would be suspicious you need some fresh mix/fert and an upsize.
Dont be intimidated by this.Lift the pot up and look to see if there are roots coming out of the drain holes. Its possible the roots could be twisted and circling around the pot.
What type of pot is it in? Give it a light water,leave to drain and then squeeze the pot(plastic) all around to loosen and the gently slide out of the container on its side.My guess is you will be full of rootball!
If you are and they are circling,you will need to root prune.Again dont be worried,use sharp secerteers!! and cut away the circuling roots,gently tease out the outside two inches of roots,so they can grow into your new mix.Remove as much soil as you dare but try not to break roots or leave them all exposed to air for very long.A gently mist is a good idea.If you want the tree to grow further,increase pot size by two inches
all around,add some slow release fert,tease your roots out and make sure the tree sits at the same height in your new pot,keep trunk clear of mix.
I add perlite to potting mix for aeration/drainage.No need to firm mix down.When you water it will firm down by itself.Do it before spring.You are in the uk,so around end of march would be ideal but you can go for it anytime.It will suffer if it becomes rootbound and then just watch for those roots coming out.Dont delay,as it causes trouble.Finally,prune the top in relation to how much you root pruned.Cut away any mushy dark brown soggy looking roots,cut to branch of healthy root. Next time you repot,if done promptly,you shouldnt need to prune top or bottom.
Dont feed from then on,until you see new top growth and only then when it is well underway,feed at half strength for some time.
Good luck dood,from a welshman in new zealand.
p.s i am a big terracotta fan.sorry about the spellling mistakes
