Getting rid of DMS, seems the usual argument for a traditional 90 minute boil, vs just 60 min (rather than hop utilisation). But I've now switched to 60min open boils, with a 4 - 5L boil off, without noticing any final difference.
I can't imagine, how just a 900ml boil off would allow all unwanted volatiles to escape (even if an opeen boil).
But, if the choice is between a small boil off, and not brewing, the answer is obvious.
If I was limited to a 900ml boil off, using 300W for the boil. I'd go for a tiny extractor, which could be battery powered PC fan with 50/75mm ducting going out the window, rather than a condenser setup.
