Heroes 5.5 WarGame Edition - Tactical Edition.

Of course, the spell description should mention that it should be used at the end of the turn, not the beginning.

We don't need to introduce artificial restrictions at the end of the turn; we can make it natural: a ritual that, for mana, establishes a movement reserve of X tiles, no more than once a day. Or the same thing in a different formulation: by spending 100% of the remaining turn and 100% of mana, gain X movement tiles (there are possible variations here: 100% of the remaining mana, 100% of the maximum reserve, or a fixed cost, but in the latter case, it will most likely be necessary to introduce an additional restriction - no more than once a day).

for example, 2000 times every three days.

It is inconvenient and not clear to count the turn in "centimeters"; I suggest switching to real tiles ("meters"), as is done in Heroes 3. Or to percentages.
Once every 3 days is also inconvenient because it forces the player to remember on which day and with which hero he has already used this bonus. And, worst of all, to keep this extra information in memory between turns.
Then it would be better to have a one-time ritual for an additional turn (once for the hero, until the next visit).

One or another ritual can, in principle, be tied to the Path of War perk, by the way. For example, a one-time ritual that, by spending the remaining turn, gives 50% movement.