Personally, I'm mostly out of the market. At this point I just do it as a habit or to create supply when I see a need. My carefully planned winter-o and purple marketers sit on huge supply, since when I have an alt who needs them, I just pick them up from the market rather than go through the hassle of emailing them.
I'd suggest just buying converters when you need them for whatever character you need them for. I try to keep 500-1000 converters on every character, and put in bids with spare slots when I log. I mean, worst case scenario, you need 1000 converters right now, you can probably buy them instantly for 100k. If you need 1000 converters right now, you can probably stomach the 20k/converter price for buy-it-now. If you can't, that's when you dip into your merit supply!
I highly doubt that email is safe for the long term, but I have a lot stored in there right now. I have a few bank mules, but even so...