When I'm working with a project that involves a lot of footage being on the timeline, the playback starts to get a delay each time I hit play. I'm not talking about dropped frames during playback. I'm talking about hitting play, then waiting 2-3 seconds for it to start playing. This greatly slows down my editing process and makes my job painful. My current project has about 7.5 hours of 3 video layers and it's lagging about 3 seconds even after using vegas's built in proxy method to replace the 4K footage with easier footage.
I suspect it's the hard drive that's lagging. I'm using an internal spinning disk 7200rpm hard drive. My computer is pretty respectably fast (8 core, 16 logical procs, Intel i9-9900K CPU @ 3.6 GHz, 3601 Mhz.)