Well you do some driving! Volvo says to inspect the transmission fluid every 20K, and to change only if said inspection warrants it. Said inspection almost always warrants it. Also, what kind of transmission fluid did you use? I was using a brand purchased from our oil supplier...wolf something or other...it was changing brown relatively quickly. I thought my transmission was going bad on my 240 with over 500K; it was a logical assumption. Had my transmission rebuilt...guess what...the fluid was still looking brown quickly. Started using Valvoline Max Life, and 20K later there was still a red tinge. We've been using Valvoline in all of our customers' cars since...and I assure myself that at 500K, my transmission needed a "$500.00 refresher".

Chris