What's up with the Borghese Gallery schedule this spring?

I bet you are seeing April 18 and April 25 as open Mondays, aren't you? Google them.

Why should the employees at tosc.it make their own lives complicate with hordes of angry tourists writing to local papers and asking for a refund?

Yep, Easter Monday is a public holiday. According to the Romewise website, the museum will be open that Monday and closed on Tuesday instead of the regular schedule. The Borghese hasn't noted this in the English section of their website but may have in Italian section; although I haven't checked.

https://www.romewise.com/easter-in-rome.html

April 25th is National Liberation Day; also a public holiday so my guess is that they're following the same open Monday/closed Tuesday schedule as for Easter. In both cases, this change from the normal schedule may be so Italians on holiday that day can visit.

Anyway, it they're selling tickets for a particular Monday, then they'll be open on that day.
\https://www.tosc.it/en/artist/galleria-borghese/ is the official ticketing source for the museum so you're in the right place.

I'M interested in seeing the Borghese Galley also, how far ahead should you purchase your tickets? 2weeks? 1 month? 2 months?

Might depend on when you're visiting? If going during high or shoulder seasons, the previous rule of thumb was to book as soon as tickets become available, especially if having a preference for a particular date and time slot. Ticket used to be snapped up very quickly! Will 2022 spring/summer/fall visitation numbers be anywhere close to pre-pandemic? It's anyone's guess but better safe than sorry?

I'm due in Rome on April 21 but am not ready to start buying nonrefundable things like sightseeing tickets yet. Too much could go wrong. But that's an individual decision.

I agree that it matters when you're traveling (will it be a peak period?), but the number of days you have in Rome will also be significant. A 3-night stay gives you less scheduling flexibility than a 5-night stay. Will one of your days be a day when the gallery is closed? And do you have plans for other difficult-to-schedule sights--like the Vatican Scavi entry, lower-level access at the Colosseum, or the Domus Aurea? Needing to put a bunch of puzzle pieces together could complicate matters.

I'd recommend at least keeping a close eye on ticket availability for the Borghese. What does it look like for this week? Next week? The week before you'll be in town? Your days in Rome? If you do that, you should be able to see when it's essential to nail down a ticket.

But also consider how essential the Borghese is to you. Perhaps it's so incredibly critical that you don't mind risking the cost of admission by buying your ticket as soon as you can.

...not ready to start buying nonrefundable things like sightseeing
tickets...

Agreed. Risk-averse travelers might be less inclined to spring for non-refundable/non-changeable tickets too far in advance. It's a good suggestion to keep an eye on the site for how quickly tickets are selling as your trip dates approach.

Thank you so much Kathy for mentioning the holiday schedule!!! That answered my questions.