Chapter 8 is intended if you are not using Rolemaster. But if you are using Rolemaster, the spell lists do get harder to develop as you go up levels. Rolemaster tends not to say "you can't", it typically just says "it costs more DP". The actual rules for this are in the RMSR on page 60-61 (especially see table T-2.4 on page 61). For a pure caster, base lists always cost 3/3/3, while open lists cost 4/4/4 up to level 20 and 6/6/6 thereafter, and closed lists cost 4/4/4 up to level 20 and 8/8 thereafter. So it's easier to get those lists to 50 if you make them base lists, but it's not required.
