When do I determine if my husband who I am caregiving for need assisted living?

Caregiving. Being in a caregiver role is very difficult. Even though you love your husband, he may need more care then you can provide by yourself. Only you know how this is for you right now. But it could help to review your situation w/a geriatric care manager. They're trained to assess what's needed & how best to provide it -- http://www.Caremanager.Org/why-care-management/what-you-should-know/.
Subjective. It's hard to know as the answer is different for everyone. Basically when you feel overwhelmed, you feel like your husband's care may possibly be compromised by your lack of time, energy or overall fatigue. It's hard to give up that aspect of care to someone who isn't family as its very hard to find someone who will genuinely care and do as much as family.