The Moistness Angle - Need a lifer's perspective

Since my first grow February of last year I had four crops; an outdoor and three indoors. My outdoors crops were unremarkable. Business as usual, but I have experience growing outdoors. It's the indoor crops I'm noticing a problem with. You see, I live in a part of the country where humidity is damn near a foreign word. In fact, the main reason I hear for people moving here is the 'dry heat'. After morning hours, the RH rarely ever goes above 30% and most of the time, it hangs out in the low teens. I tried a baby humidifier, but it was too much job for the small unit. Since then, I haven't bothered with it.

Now, my problem; what I've noticed in the few crops that I've grown is that the plants seem to have a prolonged flowering time eg they take longer to flower than they're supposed to. Plants that should finish in 65 days normally, still aren't where I'd like them after 75-80 days and plants that should finish in 12 weeks look like the could've gone 2 more.
What I'm wondering is if it's possible that the low RH of my grow room is prolonging the flowering time of my plants and also, what are some other factors that can prolong flowering times?

any stress will prolong flower time. if you transplant the day you switch them to 12/12, it can take an extra week or two. the plant will give energy to getting over the shock before using sugars to fruit. i try to avoid ANY stress for at least a week before going 12/12. ive never heard of low humiditymessing with a flowering cycle. id love your %30! i have a super sulver cheese i have to ut early every time because the buds get too big and dense and the moisture causes it to fuckin mold because its so fat and dense. i run a negative pressure flowering room tho, and its rainy out. cant wait for summertime

I dunno how much it affects flower time but putting your potted plant in a bigger pot filled with peat moss sphagum that is kept damp will help. A laundry basket might work with some mesh to keep peat moss in