I can't find any timelines, but I recommend being aggressive with your Regional Office to make sure they're even working on it.
Here's why: The BVA awarded 20% disability Sep 2017. The BVA sent the Judge's decision to the RO 11 Sep 17 and no action. I faxed the RO a copy of the BVA letter (they acknowledged receipt) on 18 Oct 17and still no action. I mailed the RO a 2nd copy of the BVA decision on 14 Dec and still no action. January 18, I got the national office to press the issue, the RO reported they didn't get the BVA letter until 14 Dec and still no action. It's now 2 Feb and I'm still in the dark.
Here's my long "whining to myself" version:
After a 6 year fight, the BVA awarded 20% disability Sep 17. I checked with my RO to ensure they had the decision letter. They told me they did not receive the BVA decision and asked me to fax it to them, I faxed it, they acknowledged receipt on 18 Oct 17 and would start working it. I asked again in Dec, they sent me a letter that they knew nothing about it, which was insulting since they already acknowledged they received my Oct 17 fax and would work on it. The first insult. So, I mailed a 2nd pristine copy to the RO, they received it 14 Dec. I checked again mid-Jan, no answer whatsoever. So, I asked the national office, explained it all and offered to send them the proof of what was happening (I always work via e-mail where possible and keep all copies). The national office reported the RO got a copy of the decision on 11 Sep 2017. The national office then sent me a "correction" e-mail and stated the RO didn't get a copy until 14 Dec. Another larger insult. Although the RO acknowledged receipt of the decision letter on 18 Oct, and the national office knew about it, the national office went along with the 14 Dec date. So, I asked the BVA when they sent the letter, and I'm not kidding, the BVA strongly implied (without actually saying it) that they don't track decisions or know what happens to a decision once it's made, which was the insult that topped the other insults and was clear, absolute BS. So, now the RO has three copies of the BVA decision dating back to 11 Sep 17, I've heard nothing and strongly suspect when I ask again, I'll go back thru the same loop.