I usually max myself out around 200-250K before I splurge and spend them on reward nights during a vacation. Use them before you lose them. I remember when almost all HIE's were 10,000 points only. Then many of them, at least the ones I stayed at, jumped to 25,000 points. I had just over 100K at that time which was good for 10 days (I was saving up for a 2 week vacation), then boom, it was only good for 4 days.
Once I hit my threshold of about 200-250K, I switch to earning miles for the rest of the year until I use the points up.