An authorization places a hold on the funds and is valid for 29 days.
After a successful authorization, PayPal recommends that you capture the funds within the 3-day honor period. Success of the capture is subject to risk and availability of funds on the authorized funding instrument.
Within the 29-day authorization period, you can issue multiple re-authorizations after the honor period expires. A re-authorization generates a new Authorization ID and restarts the honor period. Any subsequent capture should be performed on the new Authorization ID. If you do a re-authorization on the 27th day of the authorization, you get only 2 days of honor period.
You can capture less than the original authorization, full authorization amount, or even more than the authorization amount (up to 115% of the original authorization or $75 USD more, whichever is less).