How long do you think the last tier of Legion will last?

For reference:

Naxxramas - 210 days and 19 bosses - 11 days per boss
Sunwell Plateau - 233 days and 6 bosses - 39 days per boss
Icecrown Citadel - 364 days and 12 bosses - 30 days per boss (RS lasted 161 days which makes 161 days for 1 boss)
Dragon Soul - 301 days and 8 encounters - 38 days per encounter
Siege of Orgrimmar - 429 days and 14 bosses - 31 days per boss
Hellfire Citadel - 435 days and 13 bosses - 33 days per boss

Based on that, I expect the last tier of Legion to last roughly 14 months, roughly a month per boss. Your opinion?