not all no-rinse sanitisers are equal, ive had experience with 3 types, a Sodium Percarbonate based one from the lhbs which cost circa £9 per kilo Videne ansd starsan.
the Sodium Percarbonate based sanitiser had a 10-15 minute active window and was spent after that time, i assume due to it maintaining a hi o2 saturation level for a limited period once mixed up but i am no chemist. the tub didnt last very long as it needed mixing up at different stages during the brewday and when kegging/bottling.
Videne which comes in a 500ml bottle and is iirc applied at 1.25ml per litre is very economical and after 12months of use i still had just under 1/2 a bottle left, however its not a persistent sanitiser and soon becomes spent, an indicator of when its spent is when the solution looses its red/brown tint and is again a clear colourless liquid.
starsan is what im using now it is more persistent and only needs 30 seconds or so of contact to be effective, at 8-10ml to make up a 5l solution its very ecconomical an indicator that its no longer active is if it turns cloudy, though that can happen with hard tap water as soon as you mix it, a much clearer indicator of its potency is checking its ph with an indicator strip and as long as the ph is 3 or lower its active.
if applied with a trigger spray bottle 5l can last months, even with kitchjen use as the starsan is much cheaper than the detol etc surface sanitiser sprays
as we have hard water i mix up with 5l of tesco ashbeck water at a £ per 5l.. my vote is for the starsan for best vfm and simplicity of use.
even when you consider a £ for a book of ebay indicator papers and using 5l bottles of water to mix up,