2004 Honda Odyssey = around 5-7k, which is usually 4-5 months. I always forget to reset the maintenance minder, otherwise I'd use that. The maintenance light/indicator seems to suggest 7k intervals. Use 5w-20, usually synthetic.
2002 Mazda Tribute 3.0 V6 = around 5k as it doesn't get driven very much. Works out to about every 6 months. Use 5w-20 or 5w-30 conventional.
1996 Nissan Maxima 3.0 V6 = around 5k, use synthetic or a syn-blend 5w-30 or 10w-30 in this one
1985 Ford F250 460 V8 = usually 3k (it also doesn't get driven much) or whenever I feel like I've mixed too many different types of oils through it as top-up. It has a leaking rear main, so I usually top-up with whatever bottle of oil in the garage that has the seal broken. I try to do a change in early summer using 15w-40 HDEO, then a change in early winter to 10w-30 HDEO. That works out to about 3k intervals.
All our vehicles are mostly highway miles.