One of the three remaining Project 667BDR submarines, Ryazan, has returned to its base in Vilyuchinsk after an overhaul at the Zvezda plant in Vladivostok.
The submarine was transferred to the Pacific from the Northern Fleet in 2008. It began its overhaul in 2012 and its return to service was delayed a number of times.
Ryazan is an old submarine - it began service in 1982. It is not clear what is the reason submarines of this class are kept in service, but they seem to be doing reasonably well. Each submarine carries 16 R-29R missiles with three warheads, so the return of Ryazan will increase the New START warhead count.
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It looks like they are keeping some reference amount of submarines in mind (14 for kind of pseudoparity?) and want to keep the DeltaIII to reach this amount as fast as possible, and then probably put one out of service for every new coming Borey (and have 6 DeltaIV + 8 Borey = 14 in the end). Then it was reasonable to overhaul Ryazan - she is the junior of DeltaIII, and would be replaced with the last Borey in the some 2022, or even later... Or maybe they have 15 in mind :-)
The SS-N-18 missiles continued to be made with great dispatch in the mid-nineties:
http://www.pravosudie.biz/base3/data_ue/sudwsggbv.htm
Perhaps, so there is a lot of these rockets in arsenals that it makes sense to keep old subs... (???)
Tula (667BDRM) has return to the North Fleet after an overhaul in 2017, and Bryansk to go to repair on the Zvyozdochka plant:
http://function.mil.ru/news_page/country/more.htm?id=12114579@egNews