pinching out sweetpeas

Hi All,
I know to pinch out the tips after 3 sets of leaves but do you need to do it after that? And if so at what points


Thanks
Dmg

When do they stop flowering mum? Is it the first frost, or before?
I do want to keep several plants for seed as I have planted several varieties/ single colours so I hope a few will be cross pollinated.
I aim to have at least a dozen wigwams between the 2 plots next year.

dmg

Mine always run out of steam before the frosts - fewer flowers, with shorter stalks.