Does a month pass last 28 days or vary
Varies. If you start on 1 April it ends 1 may (30 days) and if you start on 1 may it ends on 1 June (31 days). if you start today (30 mar) it ends on 30 apr (31 days). And if you started on feb 1 it will end on 1 mar (28 days)
Today I applied a month pass I got with a stick (cost £30) and immediately went to cancel. I got the offer of 3 months for £20.
So assuming a shop voucher of £25 + £60 = £85 until 30 July so that is up to German Grand Prix.
so if on 2 August I do the same when the Hungarian Grand Prix starts that is another £85 and that takes me beyond the final Abu Dhabi Grand Prix
So £170 with minimal fuss. And the possibility of getting an email offer for early August that could make the first month cheaper.
Full season can be viewed using 7x1 month sports Pass from argos or currys
7x1 months pass would not cover the whole season it runs from March to December even with the Summer break you would need to time it right with first pass activation to get them all for less than a minimum of 8x1 month passes.