Just noticed this, and it isn't in the errata- on p.54 of ROP:M is a chart that indicates avoidance of acclimation- if you follow the description (which is unclear to begin with) it appears that lower magnitude spells provide more protection against acclimation than high magnitude spells.
How do you figure that? As far as I can tell that chart shows that high level effects are more effective than low level effects at providing protection against acclimation.
The higher the level of the effect, the fewer seasons per year it needs to be used to provide protection.
Because the text states "a level 30 effect cast by a character without a Might Score will protect a magic
character for two out of every four seasons" which indicates that a level 30 covers 2 months according to the chart while the same chart shows level 10 covering 4 seasons a year.- from the (again, admittedly ambiguous) description the chart shows how many seasons an effect covers.
The chart shows how many seasons per year the effect needs to be active to provide protection.
So a constant level 30 effect needs to be active for 2 seasons per year to protect from acclimation, while a constant level 15 effect would need to be active for at least 3 seasons per year.
The particular piece of text that you quoted ( "a level 30 effect cast by a character without a Might Score will protect a magic character for two out of every four seasons") doesn't really make any sense together with the rest of the text or with the chart, and is best ignored. (You aren't protected for a number of seasons per year. You are either protected from acclimation that year, or you are not.)
What text then supports your understanding of how the chart works for a spell effect level?
"The chart below shows the number of
seasons each year that the character must af-
fect its counterpart with its powers (based on
its Might Score), or must be affected by its
counterpart’s magic (based on the level of the
effect), in order to avoid Acclimation.
The first column shows how many seasons of
constant effects are necessary, while the
second shows seasons of effects that are ap-
plied regularly (approximately once a day),
and the last shows seasons of effects applied
only occasionally (approximately once a
week)."
In short, the actual description of how the chart works, rather than the example.
(The first half of the example: "For example, a magic character with
Might 15 would need to constantly affect a mundane character for three seasons every
year," is correct, it is only the second half that makes no sense.)
That acclimation happens per year, and either happens or not that year, is supported by the first section under the heading "Acclimation" (RoP:M p52-53)
Okay. It would help if the chart had actually been below the description instead of on the next page however.