I know there is a love hate out there with JJ glass. But I have rolled a lot of JJs through several heads over the years and never had a JJ Tube failure. The 'L' variant of the EL34 is known to have deeper, tighter lows than their standard EL34 variant and is also known to be a robust and durable tube.
If I wasn't so well stocked right now, I'd snap these up without a second thought. Great tube at a great price here!!!