TKD wrote:

Your research isn't particularly earth-shattering as for many years,
Period Travelcards haven't been particularly good value compared to
single tickets. Unless you changed mode a lot, it often made little
sense to get a Period Travelcard.

In recent years, with the push for Oyster, single fares have been
static or going down, whereas Travelcards have been increasing at
inflation or slightly more than that. This has led to single fares
(with Oyster) being even more competitive compared to a Travelcard.

The way things are going, I won't be surprised to see the slow death
of the Period Travelcard over the next few years.

Yes it will be replaced with monthly arrears billing.

How does the 1/3 discount for students affect the comparisons?

Admittedly my heavy travelling on all modes, combined with the uselessness
of Pre Pay for National Rail, makes the point a little academic.