I am 45 on the TP subscriber list and normally get my tapes as they are released. Helps to be on the West Coast where UPS ground only takes a day or two from Seattle. As I understand the production cycle, they do one tape title at a time to four slave machines. Given two tapes per issue, I would guess it takes about 2 hours (including loading, checking, testing, etc) to make 4 copies. So a full run (150 copies) of a new issue would take around 75 hours, not including all the steps involved in packing and shipping. Since the cost of inventory is extremely high (think about the cost of tape, reels, the very nice packaging, etc) I don't think they keep any inventory. So if you are ordering old titles, I think you have to wait until they have a break in the production schedule and there are sufficient orders to justify a special production run (I am guessing this may be 4 orders). Since I have a subscription, I don't have to wait.
Also, none of the principals have the TP as their main job, so for them I know it is primarily a labor of love and secondarily a business. Unlike most current business models, there are few economies of scale - I think it is closer to the old crafts, where each item is hand made.
A parallel example was my order with Quinton in Germany for their Sabina Hanks album. Their reel to reel reproduction is even smaller than the TP. It took over a year for me to get the tapes (a two volume set, like the TP). I even had to send a Euro denominated payment (no credit cards were accepted) at the beginning of the order process. Many emails later, I finally found that there was one person, working part time, who did all the real time duplications. My order was not on his top 100 things to do.
Larry