I stumbled onto Spartanwatches as well when I was shopping for a leather loop the other day. I have a third party leather loop I bought off Amazon about two years ago. It held up for about a year (and that's alternating it with several other bands). After about a year the leather started peeling away from the lug on one side. I glued it back down by applying some glue with a toothpick, but that fix only worked for a few days. Maybe better glue would do the trick, but I'm tired of messing with it. I thought about just ordering another off Amazon or eBay, but I would be willing to pay a bit more for something of higher quality that might last longer.
I have a Clockwork Synergy brown leather strap that is excellent quality, and their customer service is outstanding. I had another band by them with an older style lug that separated. They quickly shipped me a new band with redesigned lugs that has held up very well. I wear it almost every day. Unfortunately they don't make a leather loop and neither do some of the other reputable manufacturers. I was hoping Spartan would be better, but it doesn't look like they stand behind their products. I'm wondering if they are just importing the same generic bands so many Amazon and eBay sellers are importing? At least it might be easier to get a return/exchange from Spartan if you get the wrong product or it arrives defective. Most of the leather loops you buy from eBay or Amazon are shipped straight from Hong Kong and returning them just isn't worth it.
I like the leather loop so much that I would actually pay $150 for the real deal from Apple. However I own a 38mm AW. I really don't understand why Apple hasn't gotten around to making a 38mm version.
Anyway, my ideal would be to find a higher quality leather loop band by a reputable maker like Clockwork Synergy or Monowear. Unfortunately it looks like the best option for now is to take my chances again with a $20 generic leather loop off eBay, Amazon, etc. and hope it works out for at least another year.