I have had the same experience with Master Lab. All the prints I have done there are hanging on. No discernable fading or discoloration that I can see. People have said they buy cheap lots of low grade paper from the Kodak and Fuji factories in China, but I don't believe that entirely. Probably the market has reached a saturation point on digital print paper and the price of paper. And cost of output has gotten quite competitive purely from a market driven perspective. So basically they are offering a quality result for what has become a more standardized pricing point in the market.
Labs that want to charge prices that were the standard 4-5 years ago will claim they are using better paper like Kodak Royal digital print paper and/or have better equipment, and in many cases they do. Whether it has any net effect though or whether it would matter for the purposes of the prints being made is something I think people need to decide for themselves. For me, I hardly ever spend a lot of money to have prints made, I just don't see the added value for me.
IQ prints mainly with a Durst Lamda machine made in Italy as far as I know, but there are other labs that have that machine in Bangkok as well if you feel prints made on this machine will do a better job for yours needs and are looking for other options where you can get the same kind of print output made. A&B in Lad Prao, also close to Master Lab, has a Durst machine I believe, as well as a shop called Pro Image in the Din Daeng area.
Here are some details on the Durst Lambda machine and I think there are other Durst models as well:
http://www.pixelperfect.com.au/lambda.htmI have printed on all sorts of machines, including Durst, and the stuff I have printed at Master, which I think is all printed on Japanese made digital printing equipment, is high enough quality and certainly good enough for me. I printed some 20" x 24" and 20" x 30" prints there recently and they look great. Best thing is they didn't leave a whole in my pocket!