Question about auto-flowering strains

I am about to buy so new fem seeds.

This website based in the Uk has a strain that autoflowers and it says from germination to harvest is around 75 days!

Link is :
http://www.londonseedcentre.co.uk/acatalog/Auto_Flowering_Dwarfs.html

I'm thinking as I only have one grow space (I cannot have any seperate grow rooms/boxes) this would be good for me. Grow 5 fem plants, akes 75 days to harvest, then buy 5 more and start process over again.

The write up on the website says the lighting stays on 20/4 throughout the entire process. Having just completed my first grow I have a good understanding of lighting times now (18/6 then 12/12). So are they right in the amount of time and the lights?

I've grown autoflowers and am growing some now only because I had the seeds left. The short seed to harvest times advertised often do not pan out. I would say don't buy them for that reason. Also they are small plants and yield less. I grew white dwarf which was good and for a small scale grow might be just right. It is a forgiving and easy strain to grow. But it takes just as much work to grow a plant for 1 ounce as it does for 3.

thanks for the advice