This is actually not a given at all, and this is the most important thing you need to understand. Being based in Europe comes with a lot of strings attached, namely:

1) Low-cost carriers are ubiquitous and offer direct connections between almost any major city pair on the continent. If your company and/or travel agency includes low-cost options, you will be screwed out of any earnings.

2) Even with low-cost carriers out of the picture, if you have no choice whatsoever of the operating carrier, you will frequently end up strung between different alliances, especially to and from major hubs.

3) Virtually all European airlines (and frequent flyer programmes) have switched to fixed mileage earnings for intra-European travel. If you routinely end up booked on the cheapest Economy tickets, your mileage accrual may be way less than you expect. For instance, 200 flights in low Economy on Lufthansa Group will net you a mere 25-30k miles in many Star Alliance programmes (and zero in quite a few others!). This isn't enough even for Star Alliance Gold status, let alone the top tier.

In short, unless we get more clarity on the city pairs you are likely to fly and the most frequent airports you'll be flying out of, it's impossible to give a good answer. How far in advance your tickets will be booked also plays a major role.