Only a tiny bit more complex but often an order of magnitude faster with today's CPUs.
Use -print0 on find with -0 on xargs to handle spaces in filenames correctly.
GNU parallel is another step up, but xargs is generally always to hand.
find [...] - exec [...] {} +
as opposed to
find [...] - exec [...] {} \;
worked fine and was performant enough for my use-case. An example command was
find . -type f -name "*.html" -exec sed -i '' -e 's/\.\.\/\.\.\/\.\.\//\.\.\/\.\.\/\.\.\/source\//g' {} +
which took about 20s to run
find . -type f -name "*.html" -exec sed -i '' -e 's|\.\./\.\./\.\./|../../../source/|g' {} +
If your sed is GNU, or otherwise sane, one can also `sed -Ee` and then use `s|\Q../../../|` getting rid of almost every escape character. I got you half way there because one need not escape the "." in the replacement pattern because "." isn't a meta character in the replacement space - what would that even mean?