Hey Maria,
I'd say it depends on what you're planning on using the elastic IT for. I used to use regular thread but I always snapped it as well, do I bought a dispenser of mesika elastics (IET).
Whilst it is more visible than regular IT, it's much stronger, strechier obviously, and I think easier to use because you don't need to strip it from a bunch of other fibres.
I would DEFINITELY recommend "S.T.El.Th" from NUMS (
http://www.nothingupmysleeve.com) as you get a brilliant system to tie your own loops (great little devices for many effects) and you get a great IET called "Silk Worm" which is better in my opinion than Mesika's thread as it's a hell of a lot stronger!
Unfortunately I tangled up my silkworm spool and I'd only used it for a few loops, but now I can't use any more!
So yeah, invest in that system as it saves you from wasting hundreds of pounds on loops manufactured using mesika's weaker loops!
Rant over...
Hope I helped but ask any questions if you like.
Fabian.