I'd prefer to avoid external services.
why my node should go out of sync? I use it for other personal services (so I take care of it), my hardware il reliable (except for the UPS, I must replace it). my home internet connection is not the best in the world, but this would remain a problem because I run the Telegram bot from the same connection.

Moreover, these services might use different estimation algorithms from Bitcoin Core, I should do some research to understand which algorithm gives the best estimation