Linda,
Actually my situatin quiet same wth you, i have more than 10avent bottle which i prepared before my boys out. but , you know what happen to my bottle now? some of them stean and steam become blur atthe inside bottle as i use them for put my ebm when i pump put, i thrown away half, some i still keep. i try to give my boys to use but they dont like it, too hard of the teats, drink very very slow and need to use more breath to finish up, ned abt 1 hour . So i give up,as you know my boys was prem baby and they have problem for breath too, too tired for them if i continue to give them the hard teat. Actually, the first bottle they use if fiffy bottle which got hole for air come out, for them easy sucking when they drink. After that i change to Dr.brown(thin& long type) as the have the tube inside was easy for my boys for suck the milk, and they like the bottle and can finish quiet fast, less wind. After that, i thinking to change to neck type for them as i use avent steamer, if fat type more easy when steam. My friend recorment me Bfree, she say Bfree bottle more strong than Dr.brown bottle, so i decided to give my boys Bfree, at first i only buy the teats which avaouble flow to try first, i use avent bottle, actually ok, no leacking, but they drink very slow, because they use to use the bottle got tube inside which more easy to suck. My boys very lazy one. So i still cant use my avent bottle. no choice la.. i buy the Bfree and now all was using Bfree. Very good and less wind. more easy to suck. Actually, you can leave the avent bottle there, maybe wait they big than give them, somemore you one free, mine one all need to buy, but i put aside there. Try to give baby the best which easy for them one, dont follow our way, which way you think he more easy and more comfortable than give him that one.
If he use avent the sats drop than better dont give him, just buy the bottle got tube inside, more good for baby who have sucking problem. this is my advice. ya, i but the Bfree bottle and teat in 20% discount at kiddy palace, dont know still have or not the discount, i just buyed last month, you can try to ask, i buy to keep stock as got offer, i have 10teats and 4 new bottle. If not you can but at kaki bukit there. they open until 9.30pm.
yeah breastfeeding makes me stress. I'm sorta torn between wanting her suckle more so get more BM and letting her rest coz drinkin FM is quicker.For us, BM takes longer. 
