two Guppy questions

I am crossposting this with alt.aquaria and also freshwater.misc........

I just got a trio of guppies for my 5 gallon bow front as I heard you should
have 2 males to every 1 female to cut back on stress from the constant
chasing to mate. One female is turquoise and black, the other female is
purple and black. The male is purple and black too. One female already has
a small black gravid spot, I'll estimate her at 1-2 weeks along.

My questions are I read gestation is 3-4 weeks, most saying 4 weeks. One
site had a comment that this timeframe depends on the temperature of the
tank. Is this true and how would temperature make the difference and what
is the difference? My tank is 80 degrees.

The second thing I read was that if your tank has brighter light or even
grow lights, this speeds up their mating and they can have fry as soon as
2-1/2 weeks. True?

Also, I plan on keeping these babies and I have a breeder containment to
put in my 10 gallon when I think the time is getting closer. Having guppies
in the past I know they usually get very large, sort of bursting before they
actually release the fry. So I hope I time it right. If anyone has any
tips please do tell.