導入機器は長く使いたいですが、保守切れによるトラブル多発やスペック不足で業務が停止してしまうと本末転倒なので、更改タイミングを考えるのが難しいです。
調べてみると、ガートナーのレポートでWEB上で公開されている物をここに残しておきます。より詳細が気になる方は、直接アクセスして翻訳かけるといいのかなと思います。
（Know When It's Time to Replace Enterprise Network Equipment ）で英語でガートナー以外にも情報がでてきます。
以下、ガートナー資料、この表の青い帯部分がガートナーが推奨する更改タイミングみたいです。
コアスイッチとかはネットワーク機器類は5年～7年のスパンですが、セキュリティ機器は攻撃に対する更新要素も多くあるようで、更改時期も3年～5年と他機器類よりも短いのが特徴ですね。
表1[ネットワーク機器の推奨耐用年数]
Depreciation:減価償却の年数
PDF引用
「 Figure 1 depicts Gartner's guidelines regarding the typical useful life of various pieces of enterprise network equipment.」
・・・
・・・
・・・
「Core Routing and Switching
In most cases, we recommend that IT organizations use core switches and routers for ve to seven
years. Replacement should not be done on a regular schedule, but should be based on:
■ Analysis of new requirements
■ The cost of operating the old equipment
■ The level of risk associated with operating long-lived network assets
In some circumstances, it may be possible to extend the useful life beyond seven years. This type of
equipment may be negatively impacted by capacity increases (for example, LAN backbone trafic or increasing WAN speeds),which may lower its useful life. Alternatively, these assets may be redeployed, for example, by moving the core switch to aggregation or access layers or by migrating midsize-branch-ofce WAN routers to smaller branch locations」・・・
Security Equipment
Security requirements can be split between threat-facing and non-threat-facing equipment. Threatfacing devices will usually have a shorter life (three to five years). Multifunction security devices
(unified threat management devices, for example) will reduce the overall life because of the
requirement to expand as one or more particular functions consume all the resources of the
appliance. Longer life cycles (five to seven years) can be attained by using dedicated function
appliances, although firewall and IPS refresh can be driven earlier by increases in required
throughput
