running ctx_ddl.optimize_index with full optimization taking too long...can I kill it?

I'm trying to optimize a very large text index using the ctx_ddl.optimize_index with the FULL parameter and a maxtime of 120. This has been running fine with a maxtime of 30, but slowly progressing through the index. So we upped the maxtime to 120 and the script has been running for 6 hours now. I was monitoring the progress and it was processing tokens but hasn't progressed in the last 4 hours. I understand that it can go beyond the maxtime, but can I safely kill the optimize without corrupting the index?

We're running 11.2.0.3.