My <ahem> flashed HG612 has been up for 130 days straight, Huawei cab. It's very stable on my short line and copes with any throughput I can give it. Much more stable and better synch speed than those awful homehubs, works well with my Billion 7800n that seems to stay connected for around 30 days before BT's end forces a PPPoE reconnect early mornings.
I'd stay with what you have unless the 8800 has some specific facility that you need. I do have a spare HG612 and a router in case of breakdown, you may want to consider a backup set.
BT Infinity 2, HG612, Billion 7800N; 79987/19999 Kbps. Online since 1987. Macs since 1979. Dreambox fun. Advanced Radio Amateur Licence and an anorak.