MSL is an unstable field in my opinion. One of the main purpose of MSL is to provide information for drugs being marketed heavily. But the drug will go generic one day and even before that, the marketing effort wanes within 3 to 5 years. I've met an MSL for Zithromax in mid 90's.. I have no idea what he does today. I worked closely with a Fragmin MSL... I have no idea where she is today. I knew a Merrem MSL. She's a staff pharmacist today lamenting full of nostalgic MSL days of working from home office.
Though it's against my belief to be a speaker for pharma, I would think having a clinical pharmacist position at a teaching institution will allow many opportunities get on the speaker program.