I would say I have 'Two' projects, but that would be a filthy lie considering the scope of them.
Its split between a currently very active 15mm sci fi project, that really comprises of 3 projects and a withheld 20mm Moderns project (as it needs some serious reorganising and rethinking of how I'll approach it). However I also have a small 15mm Fantasy project ongoing and I plan to do a small Early WW1 project (got a British rifle platoon set up, but haven't done anything else).
When Forged in Battle release their 15mm Ancients, its likely i'll buckle and start another project.
However for the time being I'm almost completely concentrating on the 15mm sci fi. Once I have finished I may move on to completing my reorganized 20mm Modern USMC and Iranians. Or I may start another 15mm sci fi force.
Of course real life is about to get very busy starting a Masters at Uni, so I may be stuck on the 15mm sci fi project for ages
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When it comes down to how many projects you have, I suppose its all relative to what you want to achieve (size of the project etc), time and money.