Here is something I've seen on this topic that may be worth paying attenton to. As RobertC mentioned, most turbine oils have been reformulated with Grp II over the last decade or so. As operators top up with the reformulated product, they have occasionally seen deposit formation or filter plugging as the process progresses. This is due to the reduced solvency of Grp II relative to Grp I base oils. (The price of better oxidative stability is reduced solvency for mineral base oils.) Crud that was being held in solution by the older formulation beings to fall out as the proportion of the newer formulation increases.
It's just something to be aware of. If it causes significant operational problems, the operator may want to consider additional filtration options, particularly something like an electrostatic or BCA filter. Or just bite the bullet & drain & refill. Still, the lower solvency of Grp II is not going to change, and while oxidative crud will form more slowly, it will still form. Maybe best to get the high-tech filter and be done with it?