Consider increasing proposal creation cost by 1HBD for each day it "lasts" over 10 days
Motivation: discourage "long term" proposals from lingering in the proposal list without good reason.
For example, to create a post that "exists" (end_time - creation_time) for one year would cost 356 HBD (356 days). Proposer can increase their payout by 1 HBD per day to cover this cost (assuming their proposal gets approved).
This may encourage posters who are not sure they will get funded to created shorter term "milestone" type proposals (e.g. phase 1, phase 2, etc), instead of creating one post for the entire development interval. Of course, each of these subsequent proposals would need to be voted-in, but this would also allow for more oversight of the project.