DS is 18 months and will be very soon too big for his existing nappies (MEOS and Bambinex Teddies). He's 98th centile for height & weight, weighs about 32lbs and has a pot belly & chubby legs. 
DH has been asking whether it's worth buying size 3 nappies & XL wraps or whether it'd be cheaper to go disposable :(.
I doubt DS will be ready for potty training for a good while yet. We do EC and he'll usually tell me when he does a wee / poo while he's nappy free, but only after the fact, not beforehand. He doesn't actually 'perform' in the potty though.
Am I likely to get my money's worth given that if we have a second DC they may not even need size 3 nappies? (DS is big, but neither DH nor I are particularly big or tall: both 5'7ish average build.)