crikey - yes, one does go slower off road, this is why I also gave the time, about 20hrs
An 80mile road side sounds like about 4-5hrs of riding. A bottle is typically 750ml or 500ml, this gives a maximum rate of fluid intake that is less than 200ml/hr which is not enough for any sort of exercise. The question was about long rides specifically, and this is very clearly not enough for sustained effort of any sort. Even in winter.
As for need ing to drink watching TV as an indication of not drinking enough whilst riding? I think you'll find you need to drink when not in the bike to stay hydrated. 4-5hrs of doing anything is thirsty work.
As I said, yes it is possible to ride for this long with a bottle, and I am sure that you and a lot of people on this site could do this, maybe even with drinking nothing, but it will be comfier and certainly easier when properly hydrated. This applies to all human beings, bar none.
Dimmadam - as you correctly pointed out, bottles of energy drink are an alternate and equally appropriate way of fuelling and hydrating your body. I found this did not work for me so can not comment on quantities etc. to answer the original question. However for short rides, to minimise the amount of separate items I have to carry I do go with a just a bottle as you do sometimes. I just like eating too much to sustain this for longer periods and the "reward" of some food when going with solid energy seems to work better with my head. As you say, stopping for lunch, and then trying to get back on the bike with a belly full of pub grub is a nightmare and can be a ride wrecker