that 8 hrs of night sleep is really supposed to be an 8 hr stretch...until 18 mos, most bubs work best on an overall 12 hr day and 12 hr night.
For a 1 mos old, average A time is really about 1 hr to 1 hr 15 - and that includes eating, winddown and time to fall asleep. So I wouldn't try for 1.5 hrs tomorrow. Also, most bubs have their shortest A time first thing in the morning, so that one may even be a bit shorter.
With waking at 40 min, I'm guessing he's just having trouble getting himself past the jolts between sleep cycles. When he wakes at 40 min, is he crying for you or just fussy? If he's just fussy, I'd wait and see if he settles himself. If he's crying, have you tried extending him by using pat/shh? Is he swaddled? If not, that should help. If he is, you can try w2s and go in at 30 min and "hold" him through the jolt at 40 min.
hth
michelle