It would depend on the legal details of your employment. If you are working in Canada, say for the Canadian office of a US company, and it's very clear that you are a Canadian employee, then visiting once a month would cause no issues at all.
However, if you are the only employee in Canada, and that company is essentially a US company with no base of operations here, then CBP gets more suspicious. You aren't supposed to "work" on a B1 visa. You're supposed to be visiting your head office for meetings/training/etc. If you're a remote employee working out of your home office, and the rest of your company is in the US, you can expect questions if you go too often.
I worked for a large US company, and I flew to the US 8-10 times a year. I never had issues.. but in my case, the US company had a Canadian HQ, multiple locations in Canada and employed more than 8,000 people in Canada. You've heard of this company. Everyone has.
CBP would ask me why I was visiting, and I'd say "Going to Corp HQ for quarterly meeting", and they would stamp the passport and wave me through. I never once had a follow up question.. well, maybe something like "how many days are you going to stay", but nothing more serious.