Are there consequences to setting this value that high? (How can I determine a good value)?
Using r.SkinCache.PrintMemorySummary is the best way to determine the amount of memory your scene requires. Increasing the r.SkinCache.SceneMemoryLimitInMB is more of a concern for real-time games where maintaining a memory budget is a critical. Because you are rendering out a sequence of frames you are only limited by hardware and time. Practically speaking, render highly complex scenes can take longer to render on the GPU which can cause TDRs, but you can often increase your TDRDelay to workaround that issue.