I remember a discussion in here last week about expiration running long.
Someone mentioned 3 hours a day.
Someone at IBM told me once that it was more efficient to run it once a
week  (apparently, there's a lot to look at in review, if done every day..
it doesn't buy you much).     So I switched mine at that time to run once a
week and saw a huge improvement.
We have 3 ADSM-MVS servers, running 3.1.2.14.    All 3 are between 6 and 9
GB.   All 3 run expiration once per week, taking between 1.5 and 4 hours.
Julie