the time is roughly the same for form1 and 4's. The suggestions about doing a trust still apply to both a form 1 and 4. On a trust you can let others use it when you are not there, for example my bother is a trustee on the trust.
For a form 1 to be 'worth it' over buying a can you have to have a few things. You have to already have the equipment to build it. It's not cost effective to buy a lathe or drill press and tooling to only build 1 can. If you are going to build multiples, maybe. If you already have the tools it is very cost effective. You can go the solvent trap route, or you can turn your own parts in a lathe.
Setting aside the cost of machines and tools, and assuming you already have them, you can save a lot of money and build a high quality can. Without a lathe, just having a drill press and going with solvent trap parts or even freeze plugs, you will pay about $200 dollars in parts and an additional $200 for the stamp. So $400 all in on a titanium can that will work on any center fire rifle up to .30 cal non magnums. Compare that to an all titanium can from a manufacturer at around $1000.
If you have a lathe, you can buy the raw materials. I have built cans for .30 caliber, all titanium with 17-4 blast baffles for less than $300 including the stamp. That's less than $100 dollars in parts. They work very well on .22 center fire as well.
In my opinion, building just one can isn't cost effective. just buy what you want and move on. If you plan to have several, especially if you already have tools, you can save a bundle.