I worked out in our situation it was never worth weekly/monthly tickets, only PAYG or annual. But with annual the gain was so small that it wasn't worth the outlay, especially if you had some WFH.
Similar here, based in Dartford and commuting into Charing Cross - made myself up a spreadsheet and worked out that even just one day WFH means you can start to save on the season ticket if you pick up one Off-Peak train over the rest of it.
Time-wise, we're 1hr 15min from door to desk at best or 1hr 35min if you don't catch the 'express' ones. Wouldn't want much more than that really, especially when you think a five day commute on the faster services means being out of the house for an extra twelve hours every week!
I'm fortunate that working from home is an option at least a couple of days a week and flexible hours means I can save time as well as take advantage of the Off-Peak services at £4.40 a time instead of £7.60 on contactless and save quite a bit compared to the annual option.