I think the use of Scrivenings in this way is good in pricinple, but I found recently (3.1.4.1+) that repeated searching within large scrivenings caused Scrivener to crash - for me. It has been noted here - a messy post, I admit, but it is a repeated search issue.
CORRECTION: that issue was temporary and is not now reproducible any more. Feel free to search in Scrivenings but note that dialog and F3 repeated searches work differently at present (for me at least 
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