i would go for a proper ECU remap over a 'tuning box' every time. biggest reason being the custom ecu map will get the optimum performance gains out of YOUR car and take into consideration any other changes you have made, for example, a cold air intake or sports exhaust system. a tuning box is a standard program set to advance ignition and increase fueling to any car with the same engine. there is no guarantee it will give the gains claimed and it is more likely to do damage to your engine than a customised ecu remap.
a fave company on here seems to be angel tuning, do a quick search for them on google, give them a ring and ask to speak to nigel. tell him your got his name from here and im sure he will be more than helpful. (they come to you so no worries about getting to a garage or anything)
i just realised i completely overlooked your actual question! sorry about that!
a well set up ecu chip or tuning box should not have any negitive effect on the reliability and durability of your engine HOWEVER you will likely find you like the increased power and therfore use it more regularly resulting in increased tyre wear and lower economy! thats down to how you drive tho. if you drive how you do at present you should find economy if anyting increases and tyres wear as per now.