My mates have had this problem. Offroad and first hill and they are gone. 2nd and they are in sight- 3rd and they drop back to keep me company- And 4th they have stop to adjust the gears- or have a comfort stop- or look at the pretty flowers----Any thing to stop and est those tire legs.
Pacing is what I have done ever since about the 5th MTB ride of 20 odd years ago. And that always starts as soon as the asphalt stops. Doesn't always work on the short 25 to 30 milers but pays dividends on the long ones.
Stopped the long Enduros in 2006 and went road but still get out to make the youngsters wait at the top of the offroad hills.
__________________
How long was I in the army? Five foot seven.
Spike Milligan