Milane centrale to mxp train

Validity
3 hours from the time and date of the specific train selected at the time of purchase.

and this

Use
One-way on the route chosen at the time of purchase. It is not possible to split the journey at the different stops en route. The date and itinerary cannot be changed

https://www.malpensaexpress.it/en/travel-documents/tickets/

Not sure if that means 3 hours on either side of the designated time , or 'up to 3 hrs past' the designated time.

Well this was my experience just two days ago.

We had bought Malpensa Express tickets from Milano Centrale to MXP leaving at 17:25. We arrived over an hour early and when we got to track 1 ( where the Malpensa Express leaves from) I asked the attendant at the track if we could take an earlier train. She just shrugged her shoulders and said “ Sure, any train.” (No mention of the three hour window)
So we hopped on the next train to MXP at track 1 without changing our ticket. The train was packed and our tickets were never checked in any case.

Just make sure you are near the head of the mob getting on in order to get a seat. It’s an hour ride.

I know it’s just one example but that’s our experience.

Thank you! @jennifer, you were 100% correct. We took the next train out which was 4 hours before our original ticket. Our tickets were never inspected.

Precovid, we arrived at Milan Centrale, and the train before our ticketed route was in the station. The conductor told us that we can take trains AFTER our ticketed time, but not before. Then, our ticketed train was canceled , and we had to wait another 30+ minutes for the next one. This was rather stressful, as we had a flight to catch, but thankfully we had built in enough time, and the Milan airport was easy to navigate and not overwhelming.
Just one traveler's experience. Good luck!