Sanding & Refinishing the Spar Urethane Clear Coat on Exterior Mahogany Door

In this video, I'm sanding and refinishing the spar urethane clear gloss coat on our exterior mahogany front door.
This is a solid mahogany wood exterior door, now about 20 years old (April 2021). 6 years before this video, I sanded the door down to the bare wood, restained it, and applied 3 coats of spar urethane clear gloss coat. Well, after those 6 years of afternoon sun beating down on it, the spar urethane wasn't holding up anymore. Since I wasn't ready to sand back down to the bare wood and restain this time, I decided instead to sand and refinish just the clear gloss coat of the spar urethane to get a few more years of protection before having to undertake the whole refinishing process again. I applied 4 coats of the spar urethane, spread out over several days.
The process requires a covered area with plenty of ventilation (like an open garage bay), good weather with low humidity, several days, and plenty of patience. But in the end it's worth it -- to keep a solid mahogany door that would cost a small fortune if purchased new today.
Hopefully this will protect the door for 3 (or 4? or 5?) more years, at which point I will undertake the whole refinishing process again by sanding back down to the bare wood, restaining, and then reapplying several clear coats of spar urethane.
I used the following (NOT sponsored in any way):
3M Pro Grade Precision 220 grit sandpaper;
Helmsman spar urethane, clear gloss, 16 fl. oz. can; and
Wooster Pro brushes with angle sash (for oil paints & polyurethanes).
Remember to wear protective gloves and eye protection when working with the spar urethane, and have plenty of ventilation.