Slightly longer battles: TH 2-6 3min; TH7 3:10; TH8 3:20; TH9 3:30; TH10 3:40.
I would like to see slightly longer battles: TH 2-6 3min; TH7 3:10; TH8 3:20; TH9 3:30; TH10 3:40. Partly, to help re-enable the slow style healer containg army. Partly to give more possibilities to distraction-clearing of outer buildings. Partly because the extremely rapid precise placement of troops is hard for me. However, a very long extension or unlimited would be an extreme change that is not reasonable.
It is true that currently every base can be three starred by a rapid attack (although this is more true at lower levels than higher levels). The game is biased to reward rapid attack, due to so many defenses being slow fire unlimited ammunition, due to three of the five spells being briefly helpful to unlimited attackers, and due to no troops hurting each other whether by space-exclusion or friendly fire damage. These effects already penalize a slow attack, and it is unlikely that allowing a slightly longer attack would change the game.
No one would want an unlimited attack time. Imagine being unable to play while someone takes 30 minutes to snipe every snipable building one at a time.
A longer battle time would undesirably help the poor styles of too many dragons/pekkas/giants without cleanup troops, with or without healers, but it is very unlikely that 40 seconds at TH10 would lead to TH10 being defeatable by these troops randomly placed.