The title says it all. These tulips are in about their 4th year, and are not only persisting but actually multiplying. That's unusual for tulips in this yard. The main challenge seems to be a leaf blight, which I suspect saps their energy after blooming. Maybe these are resistant? OR maybe they are just in a tulip-friendly location.
The lilacs are about 4 years old. Last year there were a couple of flowers, but this year they are making many more. So it appears that lilacs take about 4 years to start blooming significantly.
The violet is from my parents' yard in Quincy Illinois. There, the leaves are bigger and greener, and the flowers are darker blue. So climate, or local conditions, make a difference. That has also been true for sempervivum - the plants in Illinois are bigger and greener; here they have a reddish tinge.