As others have stated, this really depends on the particular needs of the project, but more importantly the ongoing pipeline of work once the initial delivery of the project has been made. if the runway behind the project isn't as big for a period of at least 4-5 months after the first delivery I would recommend avoiding hiring full-time. I would avoid the overhead and developer a relationship with a shop that has scalable resources (versus a small team or single freelancer who can only commit to responding to your work relative to how it ranks in total $$$ relative to their other work.) Generally speaking, from my experience, the % time of designers on a general project is relatively low compared to other assets or team members (all things being equal), so having a resource you can expand or contract would be the ideal solution (i.e. not going full time design hire.) The other option is to work with a shop or team that offers "dedicated" resources - which replicated the full-time accessibility of an internal hire/team member with the added flexibility of going month to month on their hiring with options to pause and then re-commence later. Happy to help in any way or answer any further questions!