I don't understand the issue. The "You feel your great strength waning" is printed every time your strength of Altas decreases. And "Suddenly your extraordinary carrying capacity fails you" is printed if it reaches zero.

Problem apeared in wilderness Strength waning warrning should be displayed few times not once with (+5) so there should be chance to recast spell before spell will stop working. I din not have chance to recast spell because those messages apeared in 1 or 2 turns.

Might be nice to use a 'more' prompt...

I've never had that happen in the wilderness - the warnings have always been issued on 5 separate turns requiring input from me. However, I've repeatedly managed to ignore the message a few times by typing too fast, even in dungeons.

However, to a speedy player it looks like the warnings are issued only once, because the message buffer updates only the one line, replacing "You feel your great strength waning" with "You feel your great strength waning x2" instead of printing a new line. I tested this out quite a few times and I always did get 5 separate warnings.

Given the almost game-breaking nature of this spell, I consider the hassle with it running out and the relative short warning period an appropriate trade-off.