Prolonged Release Pramipexole

Hi, my wife has been on immediate release pramipexole for years, alongside Sinimet, and has just started 10 days ago on prolonged release pramipexole 3.15 mg. So far so good, but worried if she gets used to this strength soon, where to go next as this is maximum strength tablet. Is anyone else on this, and can you take another weaker strength tablet with it to increase total dosage strength?
Also, what are your experiences on PR Pramipexole? Needed it as a baseline really to avoid the dreaded sudden off times, which so far has worked pretty well on the PR tablets.
Thanks for any help and advice given.