Hi spup345,
Yes … they are. In general the weak link of a mattress isn’t the springs anyway (it’s the materials above the spring) and springs that are much less costly than theirs would still be in a “good quality” range. The most important “spec” of a spring itself is the amount of steel inside it which isn’t a spec which is disclosed by any manufacturer but beyond this the suitability of a spring for a particular type of construction and for the needs and preferences of a specific person is more important than most of the specs that most people use to try and evaluate springs which are incomplete at best (see this article and post #10 here). Having said all that … they pay particular attention to the quality and performance of the springs they use in their mattresses.
I would treat them as equivalent quality/durability yes (see post #6 here). LI doesn’t make any “bad latex” and there is no “bad” Talalay latex. If it’s Talalay latex I would treat is as being a good quality material no matter who makes it.
I would focus more on the type and blend of the latex rather than asking any manufacturer who their suppliers are which is often proprietary information which they won’t disclose. While I believe they use Arpico … that could also change as mattress manufacturers will often change suppliers for many reasons. Its more important to know the type and blend of the latex than who makes it and I personally wouldn’t be worried about “clay” additives in any of the 100% natural Dunlop latex used by a reputable manufacturer (which Sleeptek is). It may also be worth mentioning that in some cases there are some types of “fillers” used in latex that can actually improve its performance so I would be cautious about taking single “pieces” of generic information and reading too much into them without the context that is necessary to “translate” them into something that is meaningful or useful in practical terms.
See post #2 here.
Phoenix