Hi Joseph,
These two phrases seems to have the same meaning in the sense of " from,since....". Normally they're interchangeable, but SOMETIMES they imply different things and give us different information when we use them.
You use 以来when you are mentioning a time or event in the past and indicating that a situation has continued from then UNTIL NOW. 自…以来 =....以来
Whereas you use 自从 when you are mentioning a time or event in the past and indicating that a situation continued from then. it only tells us when the starting point is in terms of time. it doesn't NECESSARILY imply that that situation continued from then UNTIL NOW, although we are referring to "until now" in most cases. So until when? (直到....?) the person being talked to has no idea. You have to add more information or another specific time or event to express yourself clearly.
他父亲去世以来,他心情一直不好。
He has been unhappy since his father passed away.
自从他父亲去世,他心情一直不好。直到去年他认识了她
He was unhappy after his father passed away until he met her last year. (Until when? In this case you have to add more info to let us know "until when?" Otherwise we would think you're referring to "until now".