I'm still using the Jewel fitting in my tank but i've thought about what i would do if it failed which apparently they can do a lot.
Depending on how old your tank is it will either use the old t8 bulbs or the newer t5 ones. The newer ones give about 20% more light so it may be a worthwhile upgrade if you have plants, although you would have to buy new bulbs.
That said what I was thinking of doing if it fails was making my own lid for the tank using a suitable piece of wood and fitting as many lights as i wanted. I've not checked recently but i think the light fittings cost about £20 per tube so you could probably do the whole lot for about £50/60