There are a few factors that come into play that can help.
First, some cultivars naturally produce larger traps than others- the most famous large trap cultivar probably being the B52(You can currently get these from most specialty VFT/CP retailers, they usually cost a bit more than other common cultivars). Getting a large trap cultivar will help.
Second, if you allow your VFT to goto seed, traps tend to grow smaller since the seeding process takes a lot of energy from the VFT. So cut the flowers off before they goto seed. (Also, if you cut the flower stalk off- you can use it to propagate a new cutting)
Third, make sure you are growing the plant in its proper conditions. Especially under a good deal of light.
Last, a lot of it is age related. Older VFTs usually product larger traps than younger ones, and VFTs mature fairly slow. If your traps are small despite the above- then give it a few years. If after a few years they are still really small (like, weirdly small)- then please PM me because I want a cutting
I bought a Cephalotus from them, but not supplies. I was happy on the whole- especially with both their selection and their prices. The only thing I would note is that my order took like a week to ship out. I personally did not mind, but some people might. I can say that the ceph was definitely packaged with care. They were also pretty responsive when I emailed them.
During winter VFTs go dormant. Dormancy is triggered in the fall by reduced daylength. Similarly in spring , increasing daylength starts the growth cycle again. Changes in temperature may also be a factor in inducing dormancy and regrowth. If the plants are kept wet during dormancy, they have a tendency to rot. In western Washington, you could likely keep your VFTs outside all year long.
60F during winter might be a bit warm for continued dormancy. Particularly if they are inside and the photoperiod is artificially lengthened by artifical lighting.
Even in a south facing window it may be a struggle to provide sufficient light for Dionaea to grow really well and as Bob points out, a dormant period is required. Without a proper winter dormancy, plants tend to wither away over a period of years. Gradually becoming spindly with (you guessed it) small traps.