Here's another point of view about tenure:
Yes, you’re correct in your essential understanding of tenure – “IF YOU HIRE THEM, YOU HAVE GOT THEM FOR LIFE” – though it’s really only if you grant them tenure that you’ve got them for life, other than via dismissal for cause or as the result of the “de-tenuring” process. Though rare, given UNLV’s good hiring practices, dismissal for cause does occur, often negotiated as a resignation so not widely known. Ensuring the rigor of the review of that six-year probationary record is a better solution; another is ensuring the rigor of the annual review of post-tenure performance. Effectively enhancing that rigor depends on leadership at the President’s and Provost’s level, with the resulting “trickle down” effect on colleges and departments. UNLV’s current standard for tenure and promotion is relatively rigorous, with the essential requirement that the faculty applicant must be adjudged as “excellent” in either research or teaching, at least “satisfactory” in the other area, and as at least “satisfactory” in service. Individual colleges have the flexibility, though, to vary the rigor of those labeling evaluations. The strongest, in effect, require “excellent” in at least one of those two central categories and at least “commendable” in the other. Raising that bar still further will ensure that even fewer tenured faculty become dead wood. One encouraging sign is that academic faculty in less research-oriented colleges are being held to a higher standard than was previously the case, at the university promotion and tenure committee level; another is the discouraging of summer school teaching, especially for untenured faculty, so that faculty can devote that time to productive research or scholarship that will enable a record deserving tenure.