The members are trying to tell you that yeah extending is about total extended hours but it's also (if not more so) about consistency and not skipping days. My first month extending I did the same thing with random hours on sporadic days, but after that "acclamation period" I started to dedicate 6/7 days to 4 hours of extending time. This was when i first started adding bars! I've since worked my way up to 6hrs/day for 6 days and recently started to average about 8 hours/day.
I would also add that using a Vac Mod has significantly increased my comfort level with the device and it's enabled it to make wearing it everyday more important than underpants