I used to think they were a good idea. Until I realized we have something like 5 total dues paying members, and half of us will likely be granted lifetime memberships in a couple of years for going through the line.
So pretty much all our lodge's income depends on how well (or how poorly) GL invests the endowment fund.
My lodge something like 25 years ago sold its building and bought every living member endowments. Seemed like a great idea at the time, because we could (and do) rent space on the cheap. That is, until GL lost its shirt on the market and the endowment fund took a beating. Now the investment looks a lot more iffy as compared to investing that money in a new building, then flipping it, etc.
For the individual who wants to do something long term for their lodge, sure, though I can think of other interesting things to do with $500 or so too. But when you look at it from the perspective as an aggregate investment, it gets more iffy, and those are the terms I think you have to look at it.
You also have to factor in that a lot of lodges like mine have something like 1% of its members paying dues, the rest are endowed members. So they become beholden on the endowment fund, and that has a way of working to stagnate a lodge in multiple ways. In good times for the fund, fundraising is less of a priority. Then all of a sudden when the money gets tight the brethren start tightening their belts, finger pointing and assorted drama.
Personally I think a healthier way to go about it is to have every member pay dues, but I'm not sure how to reverse the trend.