I'm not a pro on this, but it very much depends on how well the pipes are layed out. If each radiator had an independent loop to a manifold to the boiler (unlikely) you could balance each branch based on the friction (head?) to each so they all got a balanced flow. But, I don't think they often do it that way. So, the radiator that is furthest, has the most friction, and the lower flow unless it is piped with larger pipe (again, which I doubt happened).
Even if you were to be able to adjust the flows through each individual radiator to maintain an eventual steady state temperature in each room (could take a long time), the ones furthest from the boiler would take longer to heat up because of the additional mass and losses along the way - the heat by the time it got there would be lower even if the flow was balanced. This would change based on the prevailing winds and sun exposure, so it would be tough to maintain without constant tweaking.
The only time I lived where I had radiators was in Europe...the thermostatic valves seemed to work. As you can tell, I don't have much experience.