Is it possible to have too much rehearsal? The answer isn't as obvious as you might think. In British theatre most directors get four weeks' rehearsal – or, if they're very lucky and work for one of the big companies, six. Then come a couple of previews, when there's still time to fiddle with the production, then it's the all-important press night and then – well, for the director, that's usually that.

Depending on time, inclination and the length of the run, most directors continue to attend performances maybe once a week, maybe less. The day-to-day running of the show is handed over to the stage management, the performances to the actors themselves, nominally looked after by an assistant director. The show, particularly if it runs for a long time, will undoubtedly shift and change as actors try new emphases, develop confidence, find new laughs, and cement physical moves. The director can tell a lot through the running time, emailed nightly in show reports, and can of course be called back if something goes horribly wrong – but in general, in British theatre, the rehearsal time is over.

Certain directors break the mould: Katie Mitchell is known to attend performances far more regularly than most, giving detailed notes to her actors and ensuring the production she found in the rehearsal room continues to shine through clearly. Deborah Warner is another who breaks convention, and if she believes it's necessary, will continue to call rehearsals after press night. But this level of directorial attention is highly unusual.

Partly this is due to practicalities: actors are often unavailable during the day, either because they're in a new rehearsal room or taking on more lucrative voiceover work or TV jobs to supplement their theatrical income. Directors are generally paid a fee for the production, which covers work up to press night, but not usually past that. Theatres often don't have spare rehearsal space once the production is on; and things are even more complicated at venues such as the National Theatre, where shows are usually running in rep, in which case the theatre space itself might not be available.

Peter Brook's theatrical bible, The Empty Space, writes of the need never to stand still, how "the moment the actor dresses up and speaks with his own tongue he is entering the fluctuating territory if manifestation and existence that he shares with the spectator". Brook brilliantly describes the role of the audience and how, in a touring production, the space of the theatre and how individual actors and the play shift to accommodate and learn from each performance, to fluctuate and to play. Brook continues to work with his actors until the very last night of the run; his work, it seems, is never done. The sense of continuously rehearsing and exploring is still far more common in European theatre than it is in the UK. Is this a result of better funding – allowing actors and director to concentrate on one show and that alone for an entire run, or a more complex issue of attitude? Should we expect a show in the last week of a run to be identical, or at least similar to the show that the critics saw all those weeks back, or is it permissible to continue to change moves, attitudes, cut scenes as a result on an ongoing learning process?

To many actors, I suspect the idea of continuing to rehearse might seem like an insult – they understand the play and the ideas, so are perfectly able to ensure the play remains spontaneous and clear. Some even baulk at taking regular notes. In the UK most of our greatest actors have honed their craft onstage: highly experienced and attuned to the audience, often they alone are responsible for ensuring the play never stands still. But should this be the case? If a director has a brainwave about how to make the play great halfway through a run, is it disruptive for them to recall the cast and suggest his ideas? Has that time been and gone?