Inktec refill inks / cartridges

I have been using MIS ink with fairly good success. I have read on
nifty forum that Inktec ink may be better in terms of longevity. I
don't see it mentioned on this group very often. What kind of
experiences have people had with it? I see sources for the refill
ink, but pre filled cartridges seem hard to find in the USA. I have
used the MIS empty cartridges but don't like their tiny rubber plug.
Any suggestions on better empties? It seems strange that cheap filled
cartridges are less expensive than the empties. Does anyone have
experience and source of supply for the sponge less cartridges? My
cyan sponge seems to clog up much quicker than the others.

Thanks

Ray