Vacuuming has traditionally been a problem with large table sizes. In TimescaleDB we break up the tables so that they are smaller. That, combined with the new freeze map feature in Postgres (since PG 9.6: http://rhaas.blogspot.jp/2016/03/no-more-full-table-vacuums....) make vacuums not an issue for us. Certainly we've never seen this issue (even on default autovacuum settings) and we've tested some huge datasets.