Can I join BOS later?

[Hanz]

Hi. After Arc Jet systems mission paladin Dense offer me join to BOS. I want to join, but later, after Kelog's death and finish some minor quests. If I refuse his offer, can I join BOS much later?

[OutsidR]

Yes, just show up again and accept his offer which is accepted any time during game play. I have all these hours in and still is asked to join.