We recommend that our authors give their draft manuscript to beta readers at the same time as they hand it over to us to go to the development editor for review, so that you can work through ALL the feedback in parallel. If two or three people tell you a section isn't working, you know it isn't working. If one person doesn't 'get' a metaphor but another thinks it's brilliant, it's important to balance those two pieces of feedback. The development editor's read takes 2-3 weeks so we suggest that for beta readers too - that's long enough to be able to look at the manuscript in detail, but not SO long that it slips to the bottom of the to-do pile and is forgotten. (Of course, there may be a good reason why a particular beta reader might need more time, so in this as in life, you must use your judgement.)