Given that I think we need to provide even better for our wives and families, than the World, or even most of the Church, does - not just materially or physically or time-wise, but love, guidance, protection and more - I think that most men will hit their personal "wall" long before the proverbial Isaiah 4:1 '7 women'. Of course, some are not even up to one, and I think the vast majority should stop at one. Of the rest, very few of us are able to properly meet needs beyond 2 or 3 wives. In fact, I'll just throw down the gauntlet and say that in 16 years of being around Christian plural marriage, I don't believe I've yet met a man who I though would be up to properly loving and providing everything for 4 women. The men I've met with 4 or more wives, in fact, were clearly NOT up to that challenge, and thus failed miserably, in one way or another. We need to focus on the quality in our plural marriages, not the quantity.
Maybe God will raise up better men than we yet are, or have yet seen, who'll provide for 7 wives without breaking a sweat, with all 7 of those hearts going pitter-patter all the time. But I haven't seen it yet.
So your personal 'limit' is not in the Word - it's in you. If you want to raise your 'limit' - be a better husband to your current wife/wives.
See original thread and full discussion here.