my experience is that you have to babysit the senior hires a little bit more because they bring their own baggage and habits into the team even if it doesn't support the existing workflow or even goes against.
they are also more resistant to change than a fresh hire, or may be a bit more convincing when they want things to move their way (to the team's detriment).
if you want to incorporate new cultural elements into your team, especially if your team has already strong, well-developed culture, you have to be aware of what is good and what is bad within your existing team, what to keep and what to give up, and be quick to nip any unintended side effects of a cultural/workflow change in the bud.
they are also more resistant to change than a fresh hire, or may be a bit more convincing when they want things to move their way (to the team's detriment).
if you want to incorporate new cultural elements into your team, especially if your team has already strong, well-developed culture, you have to be aware of what is good and what is bad within your existing team, what to keep and what to give up, and be quick to nip any unintended side effects of a cultural/workflow change in the bud.