This depends on the subject itself, but it shouldn't be too much of an issue either way.
Let's suppose that you had practicals on Mondays yet have lectures on Mondays, Wednesdays and Fridays. This is not too much of a worry, because subjects usually have their practicals not start on the first week so the lectures and practicals will be in time for one another. The main issues with having practicals early is that A. it might be that you have a practical right after learning the theory if the subject happens to run it that way or runs late etc. (therefore it can affect your score if you don't do as well) and B. you won't get to ask any questions with those who have already done it. But the upside is that you get it done with quickly, so you can consolidate the material earlier and move on with the rest of the week. Practicals also don't necessarily run every week for science based subjects. Because tutorials often also test the theory not long after it is learned, you may find that tutorials do not also start on the first week. But once again, this depends on the subject etc. etc. but the sciences and maths as I have found usually follow the above description.
On reflection I have come to the belief that I actually like having practicals early and bunched up together (it was on a Tuesday), as tiring as it was.