When should my first tune-up take place?

[UTVitz]

The tune up consists of new spark plugs, that's it. And although toyota and may others say they are good for 120K miles, mechanics say don't leave them in the head that long or they may never come back out. My logic was if I'm going to take them out to check them I might as well replace them which I just did at 60K miles. They are not cheap plugs(Iridium), but they are superior quality to any other. About $38 for all four and it was the easiest 20 minute job I've done on any car I've owned.