I think card-clash is becoming more common, we have a card access system on all internal doors at work, plus other locations like our warehouse, and I often hear a regular beeping noise as one of the blokes downstairs struggles to get into my room because he’s got several cards/dongles, and they fight with each other.
I’ve only got one card plus my Oyster Card, and I don’t get any issues.
I usually get a notification that mine’s topped up at Hammersmith, as it’s always the first station I travel from when in That London.
Auto top-up is something you have to activate on TfL’s website, IIRC, it’s been a few years since I used the site, though.