I know this is a really old thread, but Watch OS 2 allows you to select 70 seconds for the On Tap Wake screen.
Go under Settings > General > Wake Screen in the On Tap section, choose Wake for 70 seconds.
From reading the description, it says it will stay on for 70 seconds when you tap the screen. (not when you raise your arm, which goes off when you lower your arm, as it did previously)
TxWatch