In reply to bowls: Brewster's a great trip - stunning spot and a bit of everything, starting with a river crossing straight after the car park so tip #1 - start in sandals / old trainers, stash them in the bush at the far side of the Haast river and put your boots on there. Reverse on the way back. From the hut there's a wee bit of route finding across the steepest ground on the NW flank of Armstrong around the 1600 m contour so if you're planning to do this in the dark it might be worth a recce the previous afternoon. From there it's straightforward across the Brewster Glacier onto the SW side of the peak. Once you're off the snow, which at that time of year will probably be as soon as you leave the glacier, the rock of the summit pyramid is a bit of a horror show but nothing technical. More like swimming. Anything steep enough to be technical fell off already. From the summit I followed the ridge west and over pt 2038 and Topheavy then back onto the glacier before crossing the very top of Pyke Creek (an exciting running jump as I recall.)
Time - 3 hours up to the hut, maybe. I think, from memory, I left there about 06:00 got back 13:00 ish then walked out that day but I had really good conditions on the glacier so a plan for 2 hut nights wouldn't be bad if you have the weather window for it.
Bear in mind that Brewster is right on the Main Divide of the Southern Alps so if there's any weather going, it'll get it. In particular, if there's any west in the wind it will probably rain, maybe an awful lot. Other options - The Remarkables at Queenstown - some beautiful camping spots, easy access and better weather and rock plus some rock climbing. Smaller peaks around the Matukituki Valley out of Wanaka - Mt Barff (shame about the name) from Liverpool Hut is a similar trip to Brewster with superb views of Aspiring. Mt Barth in the Ahuriri valley is another good option with a great bivi rock, according to my friends who found it. I couldn't... Hope that helps - drop me an email if you'd like any more info.