My 4.4KW system going up in a few days should, in theory, generate about 3500-3800 kwh per year, slowly dropping yearly as panels degrade.
If I use most of those, it's very good value for money at the new cap prices in October. Even using just 2000 kwh of that generation (I'll have a battery as well so I think I can do better than 2000 / 3500) it's a little over £1000 for 2000 kwh of electric.
I think you've answered your own question somewhat though, if you're on a good long term fix, then the benefit to you is much smaller. Those of us on cap pricing are going to feel the pain much sooner than you.
So you can afford to wait longer potentially anyway, because the cost of doing nothing is small enough for you.
If I can use more of that generation, and perhaps look at getting paid better for additional generation, I'm anticipating this could save me £1.5K or more per year, and that only goes up as unit prices go beyond the planned October caps.