Writing a proposal takes serious energy; only move an opportunity into stage
5 if the client has both need, interest, and allocated budget. A client stays
in stage 5 from the day you start writing the proposal to the day he accepts
it.
If your goal is 1 new client each month and your conversion rate at
stages 5 and 6 is 1/2, you need to add 8 opportunities to stage 5, every month.
And deliver 8 completed proposals to interested clients over the same timescale.
(This is where metrics start to matter. If your conversion rates earlier
in the funnel start dropping, or if there was a gap in lead gen activity in
month X, you'll suffer a reduced number of requests for proposals 3-6 months
later, and you'll have no way of putting it right.)
When they accept your proposal, punch the sky, but remember the game's
not over yet. Move them into stage 6: contract
negotiations.