If you know what your max MP is, which is a preflight item, and you do proper planning to calculate what max could be, based on the warmest forecast temp and highest point of departure then it really isn't rocket science.
Pulling into a hover gives a pretty clear idea of margin to max.
Having a giant display that says 99% isn't going to change much when too many haven't bothered to plan and ignored the subsequent low-rpm alarm.
Absolutely agree Bellringer
aa777888 - and you will of course have calculated your AUM for take off and checked that you have both IGE and OGE performance available at your operating density altitude.
Your multiple emoticons don't make it clear if you believe dirty blades can make a big difference to hover power or not. If you don't then you really do need to think again.
On big boy helicopters you get to do power assurance checks on a daily or weekly basis to check how the engine is performing and if they are good and your hover performance is suffering, chances are your blades need cleaning.