How about digital? Shoot as much as you want. See it immediately, and only keep the best. A D1 is only $5000 and you'll save the $3000 difference over a good traditional body in film costs alone fairly quickly if you shoot a lot.(posted 8745 days ago)I use 35 almost all the time - mainly because of the expense of scanning medium format from my RB67. But I find that I shoot different types of shots with each system, so I would also ask if you have really explored all the possibilities of the Pentax - or if you've just been trying to use it like a big 35. The pictures of yours that I've seen seem quite suited to medium (or even large) format. Have you been profligate with film (and more recently relying on cropping) as a crutch?
(I almost never crop by the way. In fact, I've had to force myself to open up my framing to allow for scanning and later editorial cropping. And I only shoot lots of frames in quick succession when my model is in action herself. However, one place I find the extra film of 35mm always helpful is in relaxing an uptight model. The inexperienced ones at least become extremely self-conscious when you stop shooting. I guess the real answer is several MF cameras and several assistants to keep them loaded!)