It's easier than that.

Export your bookmarls to a file ( most browsers have this function)
eMail the file to yourself ( to keep a copy say out on Yahoo mail) / or copy it to some external drive or other machine

When if primary pc is replaced, import your last export. This assumes you periodically export an updated bookmarks file.
In any even you won't start over.

If you know the file structure and have a mapped drive( some other storage device known to your primary machine) you can easily automate the process with a simple .bat file to copy the export file every so often.

Just a simple search for 'automated backup for bookmarks' turned up a boatload of hits similar to this one
which was /is for Firefox ( I personally use SeaMonkey but have 4 other browsers on this pc):

-------------------------------
set copycmd=/y
c:
if not exist "%userprofile%\application data\mozilla\firefox\profiles.ini" goto:EOF
cd "%userprofile%\application data\mozilla\firefox\"
for /f "tokens=1,2 delims=/" %%i in ('findstr /l ".default" profiles.ini') do call set var1=%%j
cd profiles\%var1%
if not exist h:\backupbookmarks (mkdir H:\backupbookmarks)
copy places.sqlite H:\backupbookmarks

----------------------------------

The H: drive reference would be the mapped drive.

Jerry