Now that we're managing to get about a year of machine washing twice a week out of the dye subbed cotton shirts with the only noticeable change being a bit of whitish fluffing up of the fibres from the washing machine and tumble dryer, we're looking at going Dye Sub for all our cotton.
Over Christmas we experimented with hot water soaking in NapiSan and hot water hand washing, and the results are so far spectacular.
As much as I like JetProSS, and IronAll, I find they just don't stand up as well as a dye subbed shirt. And people are now asking for the dye sub on cotton for casual wear and dye sub poly for sports wear.
So it looks like heat transfer will be a thing of the past for us - and I still have all this JetPro and Ironall paper :-(