I tend not to let too many points accumulate. I try to keep my accrual and spending rate about equal, since points/miles tend to lose value at a spectacular rate over the years, in my experience.
My main use of airline miles is to get confirmed upgrades. Amtrak points are used to get LD Sleeper rides exclusively.
In spite of my best attempts to spend, I still have 4xx,xxx United miles, which is just a testimony to the insane rate at which I accumulate those. And I don't even have a great deal of incentive to collect them as such since I am lifetime Gold and about to become Lifetime Platinum. It is just that between work and family trips, they add up. I cannot always use miles for family trips due to unavailability on flights of choice.
As for Amtrak, I seem to get to Select+ each year without doing anything special, and I have not considered doing anything special to reach the Select-E level, just like I have never done anything special to get to the United 1K level.
There was a period in the early 90s when I made 1K without fail for about 5 years when I was regularly commuting from Newark to Salt Lake City when I worked in the executive office of the CTO of Novell. I used to have a regular office in Novell's Orem location, four doors down from Frankenberg's office, with a wonderful view of Mount Timpanogos.