@neuric Yes, it is possible for large companies to give out such big bonuses for regular employees (especially large tech companies). My year-to-year average bonus have always hovered around 6-8 months.
The main downside however, is that the bonus is going to be based on your performance and you would never know for sure if you’re getting the higher end of the scale.
What you need to clarify is, what is the baseline expected bonus for someone who performs “on target”, and how this will be evaluated for you personally. Then you want to check how much is based on personal performance and how much for company performance.
For example, in one of my previous companies the policy was 80% based on personal performance review, 20% on company performance. Baseline for someone on target was 4 months, and for the highest evaluations it goes up to 8 months. Depending on the company this can be very transparent and open information, so all you got to do is ask.