Run for a while without a "permanent" sleeper and then you can calculate what you would lose in volume and weight.
Sort of. You'll only be loaded to your capacity. If you can fit three skids, you'll get three skid loads when two skid loads are
also available. But that doesn't mean you would have not gotten one of those two skid loads, instead, nor does it necessarily mean that you lost any money because two skids paid less than three, since the customer rents the entire truck regardless and usually one skid, three skids, or one envelope pays exactly the same. It can vary, of course, especially with each carrier.
The biggest thing about running for a while without a permanent sleeper is that you can figure out what is
and is not important with a sleeper, not only in terms of whether you want or need a permanent one, but what kind and how big you want it. One of the worst things you can do is to get a van and immediately put in a permanent sleeper, only to find out over the next few months you wish you'd have done a dozen things differently.
For a long time I drove a short wheelbase E-350, no room for a permanent sleeper. I slept on an air mattress (double-height twin from Walmart, insanely comfortable) that I inflated and took down every day. I knew my next van would be one with a permanent sleeper, because I knew that I wouldn't be able to last another year without one. Everyone's comfort level is different, but for me, continuing to be that uncomfortable out on the road would have meant not continuing to be out on the road. But also, driving that van for so long without a permanent sleeper let me figure out exactly what I wanted in one.
