When to buy train tickets

I think you're making a bit of mountain out of a mole hill on this one. The difference in price between a Super Economy ticket from Pisa to La Spezia and a Base ticket is a whole 1.50 euro. So I suggest, for this route at least, just buying tickets as you need them. No reason to stress out about an advance nonrefundable ticket. There is a baggage deposit facility at Pisa Centrale.

You are absolutely right. I hadn't realized that. The price difference isn't enough to care about it for that trip. Out of curiosity, though, if I do buy a ticket in advance that includes a leg on a regionale train, how does validating the ticket work? I'm asking because the next trip (Riomaggiore-Venice) includes a couple of options where the price difference would get up to 20 euro, which I do feel would be worth it (and my plans on this day are more definite).

Now one further question. How long is long enough to change trains? I've seen a couple journeys come up on trenitalia that give me 10-12 minutes to change trains. I know that whether 12 minutes is long enough to change trains is largely dependent on which station I'm at, but how do I find out if the station is a very large station where 12 minutes isn't enough vs a small station with only a couple of tracks? I know that airlines usually wont let you buy a ticket when the layover time is too short for that airport, does trenitalia work the same way and if it comes up as an option, I should assume that the "layover" time at that train station is long enough?

ALL tickets Regionale train tickets purchased on-line either part of a package or individual will come pre-validated. The pre-validated Regionale ticket will come with a time stamp on the ticket - ie 0800. That means that the ticket cannot be used prior to 8 AM and is valid for the next four hours. So by 1200 (noon) the ticket is dead. If buying a ticket from A to D and the train from B to C is a Regionale train then the ticket will be pre-validated to match that train schedule.

For most station, 10 minutes is adequate. You may be changing platforms or walking from one side of the platform to the other or just standing there till the next trains comes. It is pretty easy once you have done a couple. Know you train number so you can quickly check the schedule board.

If you buy a fast-train ticket online and it is linked to a regionale segment to complete your journey, you will buy both tickets in one transaction. Trenitalia will email you a ticket showing each seg,ent, possibly two separate tickets (I've received both).

The advantage to buying the whole journey in advance if it involves a fast train, is that you won't have to pay for the continuing ticket if the first train is late, you miss the connection, and have to rebook a reservation on a fast train.