We're really lucky because hubby's job is based out of San Francisco. He gets about 3 - 4 trips a year to SF. When he goes, accommodation in Silicon Valley is paid for - great suite/hotel with a good hot buffet breakfast, car hire for the time that he's there is paid for and he gets a daily food allowance. And we're 5 minutes away from the CalTrain station and it only takes 30 - 40 minutes using the CalTrain to get into the downtown King Street Station.
The frequent flyers really racks up as well. When the timing works out with my work and school schedule, me and my son will go as well. We've generally gotten 1 frequent flyer ticket out of every 4 trips he makes; so effectively, it's only 1 child ticket we have to pay for. But it does lock us into using Qantas.
We've (son and me) managed to make a trip to the US almost every 12months in the last 6 years, which usually corresponds with the annual June team (2 week) meeting for my husband's work. We'd go back to Europe in a heartbeat - but given the current situation, we're taking the opportunity to really see the US/Canada and visit as many National parks as possible. When one and sometimes two airfares; and about one or two weeks accommodation, food and car hire is taken care of in the US, it makes complete sense to go whenever we can. We then add on 3 or 4 weeks vacation to this and choose a different region to visit each time.
And yes, I do spend a lot of time in San Francisco bay area, especially around Belmont, San Mateo and Redwood Shores - but I love this city and we have a lot of family there as well. I normally end up having the car as hubby can work to the "campus" from where we stay; so my son and I always plan trips and excursions to do different things.
Plus, I'm fanatical about saving for holidays - irrespective of whether we have a trip planned or not. I allocate about a chunk of money per month as holiday money and then don't touch it (and even hubby doesn't know I do this) - and that's by really going without the things that everyone else seems to want rather than buying stuff to keep up with the Jones' e.g., our DVD and TV is old but they aren't broken so I don't need the big widescreen TV and flash TiVo system. I don't buy clothes in Australia and prefer to save the money towards US shopping. I know I'm lucky because hubby does the shopping on his trips and we save money buying clothes in the US (I do a lot of on-line browsing and he goes to the shops and checks out the sizing for me. We spend a fortune on his international MMS when this happens!

He also buys our son's clothes as well).
I also make it a point to set a food budget and then scan the catalogues for specials. I also buy in bulk (Costco has been fantastic for me in Melbourne) and when I make savings, I add it to the savings pot rather than spending it on something else. When the exchange rate is good, I change this money for US currency and I've always got some stashed away - either for our trips or for hubby when he goes.
This way, I've always got holiday money when the unexpected trip crops up without going into debt.