It typically takes me 1.5 to 2 years to complete a project but they are usually limited to rust repair/panel replacement and bolt in mods. They are not SEMA or track bound.
I do all the work including paint so I am never waiting on anyone but myself. This also helps control the cost because I can't afford to pay someone significantly more than I make to do significant amounts of work on my car. Each project is financed through the sale of the previous project. I order long lead-time parts well in advance to keep things moving along. I also order parts Sunday night to insure they are available the following weekend. Summit is great for this because you can check inventory.
I am two months into my current 69 Camaro project. The new floor and trunk floor are modified for the AME IRS and installed along with minitubs. The rear subframe is installed. I am currently installing/stretching the rear quarters. The Speartech LSA harness and 6L90E should ship this week so I will be able to figure out what sort of tunnel mods are needed. When they arrive I will order the crate engine. Anvil leadtimes can be long so I ordered the fenders etc well in advance. All I am waiting on is the rear bumper. I am constantly watching for deals on parts that I know I will need. I just picked up some new Recaro seats from a 2015 Z28 that were being swapped out for more race oriented seats.
As stated in the post above I find the key to keeping the timeframe reasonable is a realistic plan and finances in place or at least planned.
Don