Continuous merges from Branch to Trunk

If I'm to use Tortoise-SVN in a situation where I'll be wanting to periodically merge from Trunk to Branch and also Branch to trunk, how should I be doing the latter?

The "Branch to Trunk" tutorials I've come across use the "Reintegrate a branch" command, but they only ever do it once. When I try and do it a second time, I get unexpected conflicts.

If I however use the "Merge a range of revisions" command, I can merge from branch back to trunk multiple times.

The docs say that a reintegrated branch is now useless, which I guess would explain the unexpected conflicts Im getting. But if using "Merge a range of revisions" allows more than one merge from branch to trunk, why use "Reintegrate a branch" that won't?

Solution

With SVN 1.7.x you can (according to docs) --reintegrate more than once. For 1.6 and early reintegration can be performed only once
With SVN, which has support for mergeinfo (1.6+) "sync merges" may not use rev-range - previous merges are written in mergeinfo in the same revisions will not be merged again (except cases of merging subtrees in the middle, where merge become crazy of detecting ranges)
Reintegration merge performed with special pre-condition, which decrease difference between nodes to introduced only by merge-source (for giant diffs and complex changes it can be huge plus)