In addition to the comments above, it is worth observing that preliminary prospective data addressing this question was presented at AACR this year by @Kim Reiss Binder. Her group is evaluating the role of rucaparib maintenance for patients with either germline or somatic BRCA or PALB2 mutation...

I have been using olaparib as an off-label maintenance strategy for patients with germline mutations in dsDNA repair proteins. And, as a side-note, we have an ongoing trial at DFCI for niraparib for patients with germline or somatic alterations in dsDNA repair genes that extend beyond just BRCA1/2.T...

Definitely yes. However, it is infrequent to find a situation where one would stop FOLFIRINOX if the patient continues to respond. More likely, would use in situation where a patient would require a treatment break because of toxicity. Previously, would increase interval between treatments.