One has to look carefully at the potential for subjects suitable for slide film. It is not universally suitable for every scene and lighting condition. Wastage occurs through over-enthusiasm and a lack of applied knowledge to getting the best from each exposure. Things like blue casts, blocked shadows, blown highlights, uneven lighting etc., etc., can all be put down to the photographer's imprudent choice of subject, time and lack of skill. My slides are not projected (last projection was in 1984), they are printed — an entirely separate subject and skillset.
There is no harm in returning to a scene or location several times. It is especially useful for example, if the exposure you made on your first visit presents something anomalous about the scene or the lighting, or the visual arrangement strikes you as presenting more opportunities. The key with re-visits is knowing when enough is enough — when more and more visits become a minstrel picnic rather than a productive exercise in imaging. I have returned to many locations repeatedly, often because the first or subsequent visits were blighted by the unexpected appearance of people, rubbish, storms, floods or droughts (each of these often altering the scene, for better or for worse). As recently as mid-December 2024 I decided I had finished with two locations after many years of repeat visits. Other scenes and subjects I passed over decades ago come to memory as likely presenting new opportunities.
Slide film is pretty damned expensive today, and it warrants care in choice of subject and precision of exposure. Forty years ago I sustained my photography consuming Kodachrome 200 through a Canon T90. Now, one roll of Fujifilm with processing costs I think a bit more than a slab of 12 rolls of 35mm Kodachrome 200! But we are talking about money of forty years ago!
As the expense of film increases, I do have occasion now and then — a jolting realisation, if you will, to evaluate a meaningful continuation of my work in analogue. I do not shoot nearly as many rolls per year now as I once did, symbolic of changing times, increased cost, having a family and competing leisure interests — road cycling bushwalking, mountain runner and casual relief teacher. So long periods now pass with the cameras doing nothing at all.