You can quote on a request for up to seven days after it has been submitted. After this, it will no longer appear in your request inbox and it will be impossible to quote upon it.
If you have quoted on a request, your quote will stay active until an organiser has booked you or declined your quote, or until the event has passed.
We find that most organisers receive the majority of their quotes within the first few days so it's advisable to quote sooner than later!