Our Medical situation means my ds has been breastfed a bit from birth to 7 months.. but 1% breastmilk, 99% formula. He gets minimal amounts from me. As in: less than 20ml per feed (we've done weighted feeds, extensive medical investigation from birth to 5 month, 121 lactation consultant and medication didn't fix my supply, we've been through sheer hell and back to get my tiny supply established and maintained so please please don't suggest "just feed more / skin to skin / supply = demand" inaccuracies, it simply doesn't apply here, and led me into a severe postnatal depression where I thought I could fix the milk supply if only I pumped,skin2skin and hydrated more).
I've always assumed that most of the health benefits of breastfeeding will still apply to us, because at least he's had some breastmilk, right?

However my DH says he's not so sure. 10-20 ml breastmilk is never mentioned when people are talking about bf benefits.
I've always assumed that 7 months of breastfeeding tiny amounts might make up to an equivalent benefit of (say) babies who are exclusively breastfed for 4 weeks.. it some such balanced thing..
Is that actually true?
If I can breastfeed for a year with my awful supply.. is that similar to a short time of if we'd had a normal supply?
Is there any scientific basis for my assumption? Has anyone got information on length of breastfeeding in small amounts Vs the usual info on how good breastmilk is if exclusive bf?