Refilling Laser Toner Cartridges

I wonder if anyone has experience with refilling laser toner cartridges?

And how they got on?

I have just done my first refill on my HP1300 and all went very smoothly and
printing almost same as usual. The only thing I noticed is that text is
fine but feel the photos and other none text parts are a little fainter.

Someone said it could be the fact I was comparing with a print out from an
old cartridge and there will be variation from cartridge to cartridge.
Someone else said that toner does go off especially if left in a bottle and
in the light.

Any tips appreciated.

Phil