Can I buy my eSIM now and install it closer to the trip?

Yes, and it costs you nothing. The clock starts only when the eSIM first joins a network at your destination, and you have 180 days from delivery to install it. Buy today and install on landing, or anywhere in between.

What the installation window actually is

It is a figure the supplier sets on the package and sends with every catalogue sync — not a number this shop chose, and not necessarily the same on every plan. It is printed on the plan page before you buy and on the order page afterwards, and it is never guessed: where the catalogue does not agree on one window, these pages say so in words instead of picking one.

The one thing that starts the clock

Installing the profile does not start it. Paying does not start it. Joining a network at your destination does, and When validity starts goes through that one distinction in full.

If your trip moves after you buy

Trips move, and buying in March for a June trip should not be something you have to argue about in May. As long as the eSIM has not been installed, the money comes back in full — see Refund before install.