Regarding germination rates, I have found that fresh seed wil almost invariably germinate within weeks of sowing without any need for pre-treatment. This current season (I'm in Australia remember) I sowed around 15 species of tuberous Drosera of supposed varying degrees of difficulty in germination. Within 2 months I had germination of every species sown. The germination seemed to coincide with the coolest nights of fall where they received temps as low as 2 deg C (sorry don't know F). The last month of summer is always the best time to sow the seed as after germination it gives themt he longest growing season possible- resulting in the largest seedling tuber possible.
The seed that was used was all collected the season before and so was very fresh. Species included- D. macrophylla, ramellosa, various forms of D. macrantha, D. andersoniana, D. graniticola, D. bulbosa, D. platypoda, various forms of D. stolonifera, etc.
I suspect that the seed that takes years to germinate is simply old seed. Nothing can substitute for freshness- you just have to be able to get your hands on the fresh seed.....