I know this is an old post but I figure a response may help others as well.
If your doors are installed right they will probably be ok for a good long while. I had some on a 95 240sx that were not, they busted the Fenders
to hell and the inside of the doors scraped against the dash. It was miserable, I sold the car before I changed them out though. I bought it like that as a project and ended up switching jobs and decided it would be wise to get rid of it.
By the end of it the welds were almost completely a bust, from personal experience and from what I gathered from research afterwords bolt on kits work much better. You may still have to do some additional body work as far as moving the Fenders
to make sure that everything fits but a good body shop should be able to install them no problem, especially if the have a kit designed for a celica.
I would recommend making sure the kit you get is high quality, no point in getting one with bust hydraulics that will fizzle out in 3 months.
One other thing I noticed was that on windy days in particular your doors will sway when open putting extra pressure on the welds or bolts, make sure to consider how often you are getting in and out of your car, and where. Yeah you look cool as shit throwing your doors up and if you meet that one person that's dumb enough you can actually convince them your in a Lamborghini (no joke, actually happened), but you also scream that you have a little money in your car and in certain neighborhoods that gets you a smashed hatch and missing speakers. Also in general they do get a little annoying because you have to lift them and you end up with lots of finger prints at the bottom of your door for no apparent reason to outsiders.
On the other hand if your building a flashy car that may hit a couple of shows and you really don't make a lot of stops and get in and out of your car very much they really are clean as hell. The 240 I had them on was slammed on 18s with a full lip kit, blacked out windows and some kind of pearl paint. Although Im pretty sure it was less on purpose and more because whoever painted it decided painting it 6 different colors was a good plan. It was a serious project. The bottom line is they draw attention and if thats what you want, they will get it.
Look at it less like a mod, and more like a lifestyle choice. If your area sees lots of wind and rain it may be something to consider.