Two dates are required in the Terms step of the proposal builder. Both are stated on the client's proposal, and both have real consequences.
Expires On
How long your offer stands. Pass the date without a response and the booking moves to Expired. You can send a new proposal, but you're starting the decision over.
Choosing it
One to two weeks suits most bookings. Long enough that a client can talk to a partner or check a budget, short enough that it prompts a decision.
Shorter for a contested date. If two clients are asking about the same Saturday, a shorter window tells you sooner which one is real.
Longer for a big event far out. Someone planning a wedding eighteen months ahead is comparing several DJs and won't be rushed. Three or four weeks is reasonable.
Too short reads as pressure and loses bookings. Too long means holding a date for someone who was never going to book.
Cancelable Until
The last date the client can cancel and get a full refund. After it, what they've paid may be forfeited — the deposit on a deposit booking, or the full amount on a full-amount one.
Use My Default fills this from the Cancellation Period on your profile.
Choosing it
The question to ask: by what date would it be too late for me to fill this slot?
Two to four weeks out works for most bookings. Enough notice that you could still pick something up.
Further out for peak dates. A Saturday in December that cancels ten days ahead is a date you won't refill. A longer window is justified — and clients accept it when it's clear upfront.
Shorter for quiet periods. A midweek booking in February is easier to be relaxed about.
It's not a punishment
The cancellation window exists because you turned down other work. Set it to reflect what you'd actually lose, not to discourage cancelling. A window a client finds unreasonable costs you the booking now, not later.
Where the client sees them
Both are in Proposal Terms, phrased plainly: This event proposal is valid until [date] and If accepted, this event can be canceled until [date], for a full refund.
Backing it up
The Cancellation & Refund Policy document template puts the same terms in a document the client signs. Worth attaching for anything substantial. See Adding Documents to a Proposal.