it may be worth purchasing a new cable, but if you have taken the cable off numerous times in those 2 years theres a possibility the actual connection on the earphones is worn and the cables are not holding.
this is because the cables are not actually designed to be constantly removed and upon doing so the components that hold the cable in place may have worn and gotten wider, there are cables with longer prongs but im not sure about thicker which you would require.
however you could email UE and see what they can do for you, because they are most likely out of warranty you may have to pay a small fee for a replacement set.
there is no real quick fix and if your lucky it may well just be the cable thats worn the prongs and the earphones may be fine, hence...this is why it may be worth purchasing a new cable, theres a 75% chance a new cable with new prongs will fit snug again, however the other 25% is a chance the connectors on the earphones are worn, if a new cable has the same problem you know its time to contact UE.
or contact them first anyway to see what they think.
hope this helps you, welcome to head fi and sorry about your wallet, prepare to lose some serious dosh if you stick around.