Yk mine did start sleeping more overall for a bit until it stabilised out a bit. She was pulling a 2.5hr nap and a 11hr night. Nights stared shortening so I capped the nap at 2hrs but by moving the nap later as I knew she couldn't handle the longer A to BT.
Because of this I'm always wary of a too lomg of a before BT. Pushing the first a for us just resulted in a longer nap.
If yours does sleep 2.5hrs, I'd ditch the CN and do a slightly earlier BT hun. Too much day sleep can rob them of night sleep so it's a case of finding the right balance for yours. Some prefer more DT sleep and can do just fine on 10hrs ONS, I just liked my Y time in the evenings too much! If he is a bit OT, a couple of days catch up will be great, I just don't think it'll be sustainable in the long term to expect 2.5-3hrs DT sleep and a reasonable length of night too.
Keep me posted ok? X