Front brake master cylinder

[briantheb]

Have always had a bit of an issue with the front brake.
Poor pressure and leaking reservoir lead to a replacement in  first year of ownership and period concerns have lead to regular checks of the front brakes resulting in new discs n pads and system serviced at 17+k miles.
Lever was still a bit soft with 2/3 pull in toward grip before firming up but returning to that at every subsequent pull.
Just got the bike out for first run of the year last weekend and lever comes right back to grips, pumps up a bit but after a few seconds it returns to pulling back to the grip!
Has anyone else experienced similar ?